Omega-3 fatty acids intake has been credited with many benefits to animal and human health. However, lipid addition to dairy cow diets may reduce dry matter intake and milk fat. The objective of the study was to evaluate the effects of increasing levels of microalgae rich in docosahexaenoic acid (DHA; All-G Rich, Alltech, Nicholasville, KY) in the diet of dairy cows on feed intake and milk yield, composition, and fatty acids profile. Twenty-four Holstein dairy cows were used in 6 replicated 4 × 4 Latin squares to evaluate the following treatments: basal diet, with no algae addition (A0); 2g (A50), 4 g (A100) or 6 g (A150) /kg of DM. Each experimental period included 14 adaptation days and 7 sampling days. Individual dry matter intake and milk production were recorded daily; milk samples were collected for 3 consecutive days, during the morning and afternoon milking. Data were analyzed using the MIXED procedure of SAS Inst (2001). Dry matter intake and milk fat, protein and lactose content were linearly reduced (P < 0.001) with increasing algae, while production efficiency was linearly increased (P < 0.001). Milk production quadratically increased (P = 0.053) by algae dietary inclusion, with maximal milk production of 29.77 kg on A50. Algae inclusion also quadratically increased (P ≤ 0.041) 3.5% FCM production and milk fat yield, with maximal increases on A50. DHA was detected in only 4 of 96 samples, at the higher algae doses. The ratio of saturated and unsaturated fatty acids was linearly reduced (P = 0.021) with increasing algae, while the proportion of PUFAs was linearly increased (P < 0.001). Algae inclusion reduced linearly (P ≤ 0.001) C18:0, C18:1 cis-9, C18:2 cis-9,12, and C18:3 cis-9,12,15 proportion, and increased linearly (P < 0.001) C18:2 cis-9, trans-11 proportion. Also, algae inclusion increased quadratically (P ≤ 0.044) C18:1 trans-9 and C18:1 trans-11 proportion, with the maximal increases on A150. The A50 dietary algae dose may maximize milk production and milk fat yield. Algae dietary inclusion modified milk fatty acids profile; however, there was limited DHA incorporation into milk fat.