PCU is a key point of access for primary care in Thailand. Although a community pharmacy is an ideal setting, it has not been successfully incorporated in Thailand's health service. Common illnesses are encountered everyday by community pharmacists, an appropriate compensation for this service has not been established. A primary care service of one educational institution was a study site. Eight common illnesses were emphasised. Patient visits were observed, prospectively at community pharmacy and retrospectively at PCU, during August to October 2013. Labour and material costs related to management of common illnesses were recorded. Total cost divided by total patient visits determined the unit cost. For the community pharmacy, patients were followed up after 3-14 days of visit to evaluate the effectiveness. Sensitivity analysis was performed by varying direct medical cost at ±10-30%. Findings At the community pharmacy, community pharmacists performed multiple tasks including interviewing and assessing patients, choosing an appropriate treatment and dispensing. Of 9141 visits, 775 (8.5%) with common illnesses were included. Upper respiratory disorder was found the highest 41.9% (325/755). Unit cost of treatment ranged from 54.16 baht (£1.18) for pain to 82.71 baht (£1.80) for skin disorder. Two-thirds of pharmacy visits (77.9%, 539/692) reported complete recovery. Managing common illnesses at the PCU was performed by nurse assistants, nurses, doctors and pharmacists. Of 6701 patient visits to the PCU, 1545 (23.1%) visits were at least one of the eight illnesses. Upper respiratory disorder was the majority, 53.0% (771/1454). Unit cost of treatment ranged from 85.39 baht (£1.86) for eye/ear to 245.93 baht (£5.36) for sexual health. Managing common illness at a community pharmacy shows satisfactory effectiveness with lower unit cost.