The rapid advancement of single-cell sequencing (SCS) technology has provided new insights into the relationship between inflammatory bowel disease (IBD) and colorectal cancer (CRC). This technique allows for detailed cellular analysis, enabling researchers to uncover the infiltration patterns of immune cells within the gut microenvironment and their roles in disease progression. This review summarizes significant research findings on the interplay between IBD and CRC, the characteristics of immune cell infiltration, and potential therapeutic targets identified through SCS. The aim is to offer references for future clinical studies and treatment strategies in this field.