The weaning transition from milk to solid food intake is key to the co-maturation of the gut immune system and microbiota. However, little is known on the direct effect of the initiation of solid food intake on the maturation of the immune cells. Here, we propose to evaluate its impact on the transcriptome of digestive immune cells using single cell RNA-sequencing (scRNAseq). Rabbit pups were either exclusively suckled or suckled and fed solid food from 12 days of age. At 25 days of age, mononuclear cells (n = 4/group) were isolated from the caecal lamina propria. Single live CD45+ cells were sorted by flow cytometry and droplet-based scRNAseq was performed. Data were analyzed using the Cell Ranger software and the R package Seurat. After applying quality filters, an average of 4,628 cells per sample were kept. 20 cell clusters were identified, with the majority affiliated to macrophages, dendritic cells, T and B cells based on the expression of canonical markers (CD14, CD68, CST3, CD3D, JCHAIN). Solid food introduction affected both cell proportions and transcriptomes. Namely, a marked switch in B cell populations was observed, with a strong reduction in the proportion of naive B cells (11 vs 3%) and an increase in that of mature plasma cells (2 vs 6%). Our results highlight the crucial role of the initiation of solid food intake for the maturation of the digestive mucosal immune system, and pave the way for mechanistic studies unravelling the role of the gut microbiota in this developmental process.