Abstract: Canned mackerel (Scomberomerus sp.) a widely accepted food product in the tropic, with shelflife of 3 years after production (Dec 2004-Dec. 2007) is being assessed after a 24 h exposure period under both cold (-4°) and ambient temperatures (27°). A total of 13 cans (Geisha brand of mackerel in tomato sauce) were analysed. The base line data was obtained at (0 day) with the first can. The remaining 12 cans were grouped into 2 samples in relation to the storage media adopted. After an opening the cans were kept at their respective storage media for 24 h exposure period before analysis. The readings were taken biweekly for 12 weeks. The assessment made were: organoleptic, biochemical Trimethyamine (TMA) Thiobarbituric acid (TBA) and period value (PV), microbial assay (count and identification) and proximate analysis (initial and final).The organoleptic parameters assessed were (texture, colour, rigidity of fillets and reaction of can with the product) which showed no significant variation (p>0.05) while odour, taste and appearance showed significant difference (p<0.05). The biochemical tests revealed that all parameters increased in their values in both media with increasing exposure/storage time. The ambient (PV = 4.380 meq kg^-1), TBA = 1.849 mg kg^-1 and TMA = 2.531 mgN/100 fish) were greater than the cold medium (PV = 4.300 meq kg^-1, TBA = 1.638 md kg^-1 and TMA = 2.20 gm N 100 g^-1). significant (p<0.05) increase were recorded for TMA and TBA with strong positive correlations (r = 0.61 and 0.63 respectively) with exposure storage time, while PV had a slower rate of increase with r = 0.40. The ambient medium showed fourteen bacteria sp. and four fungi sp. with a higher total viable count range of (2.8-40.7 x 10⁴ cfug^-1) as against the cold medium which had eight bacteria sp. and no fungi sp. represented with a range of (2.8-7.8 x 10⁴ cfug^-1). The bacteria growth in both media were significant (p<0.05) and present progressive increase in growth pattern with storage time. However cold storage at -4° suppress the rate of multiplication of the identified bacteria. However, the most prominent bacteria spp at ambient temperature were (a) Staphylococcus aureus (27.4 x 10⁴ cfug^-1) (b) Pseudomonas aureginosa (26.5 x 10⁴ cfug^-1) and (c) Bacillus cereus (21.5 x 10⁴ cfug^-1) whole for the cold (a) Klebisella aerogenes (6.6 x 10⁴ cfug^-1) (b) Micrococcus acidiophilus (5.7 x 10⁴ cfug^-1) and (c) Bacillus cereus (4.0 x 10⁴ cfug^-1). All viable counts recorded were still below maximum microbial count limit of (1.0 x 10⁶ cfug^-1). Canned mackerel in tomato sauce is advisably consumed before the 3 years expiry date and also immediately it is opened to prevent food poisoning. Since increase in bacteria count and biochemical values in both media with exposure/storage time were evident in this study.