In recent years, insect protein has become a popular alternative to plant protein in poultry nutrition. Therefore, it is justified to investigate how diets supplemented with such protein affect various bird species, including wild ones. This study presents the results of a feeding experiment conducted under aviary conditions on five groups of common pheasant (Phasianus colchicus L.) hens during the laying period. The birds were divided into one control group and four experimental groups, in which plant protein was replaced at 50% or 100% with black soldier fly (Hermetia illucens) meal or whole dried larvae (BSFL). Dietary supplementation with animal-derived components affected muscle group proportions and body weight, but statistically significant stimulation was noted only for skeletal development, as indicated by selected bone lengths. The most beneficial effect in this regard was observed with 50% supplementation of dried BSFL. Conversely, the total replacement of soybean meal (SBM) showed no beneficial effect on the traits under assessment. Analysis of bone micro- and macro-mineral content revealed no significant differences. Nor did the substitution of SBM with Hermetia illucens material affect internal organ mass. Regardless of the type or level of supplementation, no significant impact on disease incidence or overall bird health was observed. These results indicate that dietary supplementation with Hermetia illucens larvae protein is viable in intensive pheasant breeding, provided it does not exceed the optimal level of 50%.