The degree of spoilage of fish and beef in a daily simulated market style of southwest, Nigeria was determined by Trimethylamine (TMA) levels in each sample using the standard pictrate technique. 100g of each of the three different parts of a bull (liver, meaty and fatty tissues) and fresh African cat fish (Clarias gariepinus) (liver, meaty portion and head) were purchased twice a week for five weeks from the abattoir and Oja-Oba market in Akure respectively. The samples were subjected to ambient temperature and their degree of spoilage was assessed after 3 hours, 6 hours and 9 hours of purchase. The results showed that, there was no significant difference (P≥ 0.05) in the effect of time (hours) on TMA concentration in different parts of the fish and bull samples, though, the mean concentration of TMA in the fish samples increased with time. However, the degree of spoilage is slower in the bull compared to the fish samples but higher in the late evening (9 hours). Hence, buying and selling of beef in the late evening should be discouraged to avoid consumption of unwholesome meat with high TMA concentrations, while fish should be stored-frozen and sold in deep freezers.