Abstract: Background and Objective: Malnutrition has become a health problem in developing countries such as Indonesia. This can provide an effect on body composition, decreasing albumin levels and immunity status. Patin fish is well-known to have a high level of protein concentration and has a positive-effect on malnutrition. To investigate the effect of Patin fish protein concentrate (PFPC) on the albumin levels and immunity status of Sprague Dawley baby rat’s malnutrition. Materials and Methods: The study was a true-experiment study with a randomized pre-posttest with a control group. Thirty rats were divided into 5 groups; control of normal (K1) and malnutrition (K2), malnutrition with PFPC 13.26 (P1), 19.89 (P2) and casein 13.26 (P3) mg g1 b.wt. day1. The analysis was carried out with the paired t-test, Wilcoxon, ANOVA and Kruskal Wallis test. Results: The results showed that malnutrition has an effect on BW, albumin levels, leukocytes count and IgG levels. Post-intervention showed an increase of albumin levels in the intervention groups (p<0.05) and a significant decrease in control groups (p<0.05). There is a decrease in leukocytes count and IgG level post-intervention in intervention groups (p<0.05) and a significant increase in the post-intervention control groups (p<0.05). There were significant differences between all groups on albumin levels, leukocytes count and IgG levels. Conclusion: PFPC could improve albumin and immunity levels in malnutrition baby rats. PFPC dose of 19.89 mg g1 b.wt. day1 is the best formula in improving albumin and immunity levels.