diff --git a/__tests__/utils.test.ts b/__tests__/utils.test.ts
index 30fc61cb..8a9d01b3 100644
--- a/__tests__/utils.test.ts
+++ b/__tests__/utils.test.ts
@@ -1,9 +1,17 @@
 import * as cache from '@actions/cache';
 import * as core from '@actions/core';
+import * as io from '@actions/io';
+
+import fs from 'fs';
+import path from 'path';
+
 import {
   validateVersion,
   validatePythonVersionFormatForPyPy,
-  isCacheFeatureAvailable
+  isCacheFeatureAvailable,
+  getVersionInputFromFile,
+  getVersionInputFromPlainFile,
+  getVersionInputFromTomlFile
 } from '../src/utils';
 
 jest.mock('@actions/cache');
@@ -73,3 +81,48 @@ describe('isCacheFeatureAvailable', () => {
     expect(isCacheFeatureAvailable()).toBe(true);
   });
 });
+
+const tempDir = path.join(
+  __dirname,
+  'runner',
+  path.join(Math.random().toString(36).substring(7)),
+  'temp'
+);
+
+describe('Version from file test', () => {
+  it.each([getVersionInputFromPlainFile, getVersionInputFromFile])(
+    'Version from plain file test',
+    async _fn => {
+      await io.mkdirP(tempDir);
+      const pythonVersionFileName = 'python-version.file';
+      const pythonVersionFilePath = path.join(tempDir, pythonVersionFileName);
+      const pythonVersionFileContent = '3.7';
+      fs.writeFileSync(pythonVersionFilePath, pythonVersionFileContent);
+      expect(_fn(pythonVersionFilePath)).toEqual([pythonVersionFileContent]);
+    }
+  );
+  it.each([getVersionInputFromTomlFile, getVersionInputFromFile])(
+    'Version from standard pyproject.toml test',
+    async _fn => {
+      await io.mkdirP(tempDir);
+      const pythonVersionFileName = 'pyproject.toml';
+      const pythonVersionFilePath = path.join(tempDir, pythonVersionFileName);
+      const pythonVersion = '>=3.7';
+      const pythonVersionFileContent = `[project]\nrequires-python = "${pythonVersion}"`;
+      fs.writeFileSync(pythonVersionFilePath, pythonVersionFileContent);
+      expect(_fn(pythonVersionFilePath)).toEqual([pythonVersion]);
+    }
+  );
+  it.each([getVersionInputFromTomlFile, getVersionInputFromFile])(
+    'Version from poetry pyproject.toml test',
+    async _fn => {
+      await io.mkdirP(tempDir);
+      const pythonVersionFileName = 'pyproject.toml';
+      const pythonVersionFilePath = path.join(tempDir, pythonVersionFileName);
+      const pythonVersion = '>=3.7';
+      const pythonVersionFileContent = `[tool.poetry.dependencies]\npython = "${pythonVersion}"`;
+      fs.writeFileSync(pythonVersionFilePath, pythonVersionFileContent);
+      expect(_fn(pythonVersionFilePath)).toEqual([pythonVersion]);
+    }
+  );
+});
diff --git a/src/setup-python.ts b/src/setup-python.ts
index 69ea9d36..dc802697 100644
--- a/src/setup-python.ts
+++ b/src/setup-python.ts
@@ -5,7 +5,14 @@ import * as path from 'path';
 import * as os from 'os';
 import fs from 'fs';
 import {getCacheDistributor} from './cache-distributions/cache-factory';
-import {isCacheFeatureAvailable, logWarning, IS_MAC} from './utils';
+import {
+  isCacheFeatureAvailable,
+  logWarning,
+  IS_MAC,
+  getVersionInputFromFile,
+  getVersionInputFromPlainFile,
+  getVersionInputFromTomlFile
+} from './utils';
 
 function isPyPyVersion(versionSpec: string) {
   return versionSpec.startsWith('pypy');
@@ -22,43 +29,48 @@ async function cacheDependencies(cache: string, pythonVersion: string) {
   await cacheDistributor.restoreCache();
 }
 
-function resolveVersionInput() {
-  const versions = core.getMultilineInput('python-version');
-  let versionFile = core.getInput('python-version-file');
-
-  if (versions.length && versionFile) {
-    core.warning(
-      'Both python-version and python-version-file inputs are specified, only python-version will be used.'
+function resolveVersionInputFromDefaultFile(): string[] {
+  const couples: [string, (versionFile: string) => string[]][] = [
+    ['.python-version', getVersionInputFromPlainFile],
+    ['pyproject.toml', getVersionInputFromTomlFile]
+  ];
+  for (const [versionFile, _fn] of couples) {
+    logWarning(
+      `Neither 'python-version' nor 'python-version-file' inputs were supplied. Attempting to find '${versionFile}' file.`
     );
+    if (fs.existsSync(versionFile)) {
+      return _fn(versionFile);
+    } else {
+      logWarning(`${versionFile} doesn't exist.`);
+    }
   }
+  return [];
+}
+
+function resolveVersionInput() {
+  let versions = core.getMultilineInput('python-version');
+  const versionFile = core.getInput('python-version-file');
 
   if (versions.length) {
-    return versions;
-  }
-
-  if (versionFile) {
-    if (!fs.existsSync(versionFile)) {
-      throw new Error(
-        `The specified python version file at: ${versionFile} doesn't exist.`
+    if (versionFile) {
+      core.warning(
+        'Both python-version and python-version-file inputs are specified, only python-version will be used.'
       );
     }
-    const version = fs.readFileSync(versionFile, 'utf8');
-    core.info(`Resolved ${versionFile} as ${version}`);
-    return [version];
+  } else {
+    if (versionFile) {
+      if (!fs.existsSync(versionFile)) {
+        throw new Error(
+          `The specified python version file at: ${versionFile} doesn't exist.`
+        );
+      }
+      versions = getVersionInputFromFile(versionFile);
+    } else {
+      versions = resolveVersionInputFromDefaultFile();
+    }
   }
 
-  logWarning(
-    "Neither 'python-version' nor 'python-version-file' inputs were supplied. Attempting to find '.python-version' file."
-  );
-  versionFile = '.python-version';
-  if (fs.existsSync(versionFile)) {
-    const version = fs.readFileSync(versionFile, 'utf8');
-    core.info(`Resolved ${versionFile} as ${version}`);
-    return [version];
-  }
-
-  logWarning(`${versionFile} doesn't exist.`);
-
+  versions = Array.from(versions, version => version.split(',').join(' '));
   return versions;
 }
 
diff --git a/src/utils.ts b/src/utils.ts
index 5a5866ea..77fa8093 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -4,6 +4,7 @@ import * as core from '@actions/core';
 import fs from 'fs';
 import * as path from 'path';
 import * as semver from 'semver';
+import * as toml from 'toml';
 import * as exec from '@actions/exec';
 
 export const IS_WINDOWS = process.platform === 'win32';
@@ -181,3 +182,65 @@ export async function getOSInfo() {
     return osInfo;
   }
 }
+
+/**
+ * Python version extracted from the TOML file.
+ * If the `project` key is present at the root level, the version is assumed to
+ * be specified according to PEP 621 in `project.requires-python`.
+ * Otherwise, if the `tool` key is present at the root level, the version is
+ * assumed to be specified using poetry under `tool.poetry.dependencies.python`.
+ * If none is present, returns an empty list.
+ */
+export function getVersionInputFromTomlFile(versionFile: string): string[] {
+  core.debug(`Trying to resolve version form ${versionFile}`);
+
+  const pyprojectFile = fs.readFileSync(versionFile, 'utf8');
+  const pyprojectConfig = toml.parse(pyprojectFile);
+  const versions = [];
+
+  if ('project' in pyprojectConfig) {
+    // standard project metadata (PEP 621)
+    const projectMetadata = pyprojectConfig['project'];
+    if ('requires-python' in projectMetadata) {
+      versions.push(projectMetadata['requires-python']);
+    }
+  } else {
+    // python poetry
+    if ('tool' in pyprojectConfig) {
+      const toolMetadata = pyprojectConfig['tool'];
+      if ('poetry' in toolMetadata) {
+        const poetryMetadata = toolMetadata['poetry'];
+        if ('dependencies' in poetryMetadata) {
+          const dependenciesMetadata = poetryMetadata['dependencies'];
+          if ('python' in dependenciesMetadata) {
+            versions.push(dependenciesMetadata['python']);
+          }
+        }
+      }
+    }
+  }
+
+  core.info(`Extracted ${versions} from ${versionFile}`);
+  return versions;
+}
+
+/**
+ * Python version extracted from a plain text file.
+ */
+export function getVersionInputFromPlainFile(versionFile: string): string[] {
+  core.debug(`Trying to resolve version form ${versionFile}`);
+  const version = fs.readFileSync(versionFile, 'utf8');
+  core.info(`Resolved ${versionFile} as ${version}`);
+  return [version];
+}
+
+/**
+ * Python version extracted from a plain or TOML file.
+ */
+export function getVersionInputFromFile(versionFile: string): string[] {
+  if (versionFile.endsWith('.toml')) {
+    return getVersionInputFromTomlFile(versionFile);
+  } else {
+    return getVersionInputFromPlainFile(versionFile);
+  }
+}