Abstract: Background and Objective: The quality of cow's milk from imported races is a new subject in the field of milk production in Algeria while taking into account the new breeding conditions these animals are subjected to. Consequently, this study aims to study the effect of one of these conditions, the lactation stage, on milk physico-chemical parameters along with its impact on Fatty Acids (FA) content. Methodology: A group of 340 dairy cows were spread out over 3 dairy-farms located in the surrounding of Algiers. They were monitored for 10 month’s lactation at a rate of one sampling a month in order to cover 3 stages: Early, mid and late lactation. Results: The study showed that lactation stage significantly contributes (p<0.05) to variation of some physico-chemical parameters (acidity, density and Fat Levels (FL)) of milk delivered to local transformers. Milk (FA) profile significantly changed too (p<0.05) with a weak proportion of Saturated Fatty Acids (SFA) at early lactation, increasing very significantly (p<0.0002) at late lactation (60.73 vs. 66.16% respectively). The Short and Medium Chain Fatty Acids (SMCFA), except for C4:0 were rather in weak proportion at early lactation stage and increased during the advance of the process. However, Long Chain Fatty Acids (LCFA), particularly C18:0 and C18:1 showed an opposite tendency with a high proportion at early lactation. No lactation stage influence was shown on C18:2 and C18:3 contents (p>0.05). Conclusion: By controlling the breeding conditions, the study showed that lactation stage significantly contributes to variation in Algiers milk fat composition and alters the activity of fatty acid pathways. Besides, milk will get interesting nutritional qualities.