Background: Medication package inserts (MPIs) provides patients with appropriate information on the rational use of drugs. This study evaluated the level of conformity of MPIs with the regulatory drug labelling requirements and determined the readability of selected prescription MPIs. Methods: One hundred and fifty-six MPIs of commonly used and prescribed antilipidemics, anticonvulsants, anti-diabetes, antiarthritis and antihypertensives in Nigeria were retrieved from four pharmacies. The MPIs were evaluated on the availability of 20 items drug labelling requirements for prescription drugs by the National Agency for Food and Drug Administration and Control (NAFDAC). The readability of 31 randomly selected MPIs was assessed with seven readability measures. Primary outcomes were percentage conformity with the labelling requirements and reading grade level of the MPIs. Secondary outcomes were the MPIs sentence characteristics. Results: The percentage conformity with NAFDAC drug requirements of the MPIs ranged from 82.9% to 89.6%. All the MPIs included information on active ingredient(s), adverse drug reactions, and indications. Few MPIs, 46.8% had section on product net content and 53 (34.0%) omitted information on overdose. The reading grade level for the MPIs was 14.55 ± 1.71 (undergraduate level). Most of the MPIs, 25 (80.6%), were very difficult to read. Conclusion: The percentage conformity of the MPIs with NAFDAC drug labelling requirements was high though few vital information were missing in some MPIs. Majority of the MPIs were very difficult to read. The regulatory authority may need to optimize MPIs readability and conformity of content with drug labelling requirements prior to marketing.