Studies have shown beneficial effects of palm oil on the diet of lactating cows, with an increase or maintenance of the nutritional value of milk. However, the high levels of NDF and lignin and the lower concentration of non-fibrous carbohydrates in palm oil cake have shown negative effects on ruminal digestibility and food intake, therefore, on the amount of energy available for milk production. This study aimed to carry out a systematic review, meta-analysis, and principal components analysis to assess the effects of palm oil cake on the milk quality parameters and production by dairy cows. The search resulted in 8 references and 21 eligible studies. The distribution of data for independent variables was explored with BoxPlot. The meta-analysis was used to summarize the grouped effect of palm oil cake on milk production and quality parameters, using the fixed-effect model or random-effects model. The sampling variability assumed in the random-effects model was estimated by Cochran's Q test and the I2 statistic by Higgins and Thompson. The weighted mean difference (WMD) and standardized mean difference (SMD) summarized the size of the palm oil effect on the response variables. The factors involved in the variability expressed in the meta-analysis were investigated with the principal components analysis. The publication bias of the studies was assessed using the test by Begg and Mazumdar (1994) and Egger et al. (1997). The heterogeneity between the studies was nonexistent or very low (I2 < 3). The symmetry of the funnel graph pointed to no publication bias in the studies (P> 0,05). In comparison to the control diet, cows fed with palm oil cake showed an increase (0,19%, P <0,005) in the concentration of milk fat. In conclusion, the inclusion of 10% to 32% of palm oil cake in diets of dairy cows with an average production of 12,8 (kg day−1) of milk does not affect milk production and the yield (lactose, protein, and fat) and concentration (lactose, protein) of the milk components; and increases the concentration of milk fat by up to 0,19%.