This study was carried out to investigate the effect of equi-protein replacement of soybean meal with groundnut cake on immune status, haematology and serum biochemical parameters of broiler chickens. A total of One hundred and twenty (120) Cobb’s day old chicks were randomly allocated to five (5) dietary treatments of three (3) replicates and eight (8) chicks per replicate in a completely randomized design. The Diet I was the control diet with 100% SBM as the major plant protein source while in other diets, SBM was replaced with 25, 50, 75 and 100% GNC in equi-protein basis and designated as Diets II, III, IV and V respectively. Feed and water were provided ad-libitum throughout the experimental period of 56 days. Newcastle disease (ND) vaccines were administered following a stipulated regime. At the end of the experiment two birds were randomly selected from each replicate and slaughtered. Blood and serum was collected for haematological analysis, serum bioassay and HA/HI tests to determine antibody titres against ND vaccines. All data collected were subjected to one-way analysis of variance using SPSS software package. Results showed that haematological parameters were significantly influenced by the dietary treatments in which birds fed 50% equi-protein replacement of SBM with GNC had better PCV, basophil, MCH and MCHC values compared to that of birds in the other dietary treatments. The antibody titres of experimental birds were not significantly different among treatment groups. The diet with 50% equi-protein replacement of SBM with GNC elicited the highest antibody titres of Log28 and Log210 after the 1st and 2nd ND vaccinations when compared to the other diets. The serum total protein, globulin, albumin, and glucose were significantly influenced by the dietary treatments. The present result indicate that 50% equi-protein replacement of SBM with GNC in diets is not detrimental to health status of broiler chickens.