BACKGROUND Delayed immunologic aging is purported to be a major mechanism through which calorie restriction (CR) exerts its anti-aging effects in non-human species. However, in non-obese humans, the effect of CR on the immune system has been understudied relative to its effects on the cardiometabolic system. OBJECTIVE To examine whether CR is associated with delayed immunologic aging in non-obese humans. METHODS We tested whether long-term CR practitioners (average 10.03 years of CR) evidenced decreased expression of T cell immunosenescence markers and longer immune cell telomeres compared to gender-, race/ethnicity-, age-, and education-matched "healthy" Body Mass Index (BMI) and "overweight"/"obese" BMI groups. RESULTS Long-term human CR practitioners had lower BMI (p CONCLUSIONS We observed no clear evidence that CR as it is currently practiced in humans delays immune aging related to telomere length or T cell immunosenescent markers.