Background: The Black Soldier Fly larvae (BSFL) are a source of nutrients and bioactive compounds in broiler diets. Some components of the BSFL may serve as a prebiotic or may impact the intestinal microbiota of the broilers by other modes of action, which in turn can affect the health and performance of broilers. Here, we investigate the impact of up to 20% BSFL in broiler diets on the diversity and composition of the broiler's microbiota. Methods: Four hundred broilers were fed five iso-nutritious experimental diets with increasing levels of BSFL meal reaching 0%, 5%, 10%, 15%, 20% in the finisher diets. Eight caecal content samples coming from each of the eight replicates per treatment were collected at two time points (day 21 and day 42) for DNA extraction and sequencing of the V3-V4 regions using Illumina MiSeq 2 × 300 bp pair-end sequencing with 341f and 805r primers. Analysis of variance and Spearman's correlation were performed, while QIIME2, DADA2, and Calypso were used for data analysis. Results: When broilers were 21 days of age, the abundance of two groups of sequence variants representing Enterococcus and unclassified Christensenellaceae was significantly lower (p-value = 0.048 and p-value = 0.025, respectively) in the 20% BSFL group compared to the 0% BSFL group. There was no relevant alteration in the microbiota diversity at that stage. On day 42, the Spearman correlation analysis demonstrated that the sequence variants representing the genus Coprococcus showed a negative relationship with the BSFL inclusion levels (p-value = 0.043). The sequence variants representing the genus Roseburia and Dehalobacterium demonstrated a positive relationship with the BSFL dietary inclusion (p-value = 0.0069 and p-value = 0.0034, respectively). There was a reduction in the dissimilarity index (ANOSIM) caused by the 20% BSFL dietary inclusion. Conclusion: The addition of up to 20% BSFL in broiler diets did not affect the overall caeca microbiota diversity or composition at day 21. On day 42, there was a reduction in the beta diversity caused by the 20% BSFL dietary inclusion. The abundance of the bacterial group Roseburia was increased by the BSFL dietary inclusion, and it may be beneficial to broiler immunity and performance.