Microalgae have become an important commercial source of carotenoids and microalgae-derived functional foods are consumed by people worldwide. Therefore, an HPLC method was developed to discern the variety and content of carotenoids in the microalga Chlorella pyrenoidosa. The microalga sample was powdered, extracted, saponified and subjected to HPLC analysis. A mobile phase of methanol-acetonitrile-water (84:14:2, v/v/v) (A) and methylene chloride (100%) (B) with the following gradient elution was developed: 100% A and 0% B in the beginning, maintained for 14 min, decreased to 95% A in 25 min, 75% A in 30 min, 74% A in 35 min, 45% A in 50 min and returned to 100% A in 55 min. A total of 32 carotenoids were resolved within 49 min by using a C30 column with flow rate at 1 mL/min and detection at 450 nm. An internal standard beta-apo-8'-carotenal was used to quantify all the carotenoids. All-trans-lutein was present in exceptionally large amount (125034.4 microg/g), followed by cis isomers of lutein (27975.3 microg/g), all-trans-alpha-carotene (2465.8 microg/g), zeaxanthin (2170.3 microg/g), cis isomers of beta-carotene (2159.3 microg/g), all-trans-beta-carotene (2155.0 microg/g), cis isomers of alpha-carotene (1766.7 microg/g), beta-cryptoxanthin (334.9 microg/g), neoxanthin and its cis isomers (199.7 microg/g), neochrome (65.2 microg/g), auroxanthin (38.5 microg/g) and violaxanthin and its cis isomers (38.1 microg/g).