This study investigated the connection between mental age and human figure drawings (HFDs) in adults with intellectual disability (ID) using Viktor Lowenfeld’s six artistic stages of development (scribble, pre-schematic, schematic, realistic, naturalistic, and adolescent). Participants consisted of two individuals recruited through a local health services agency, who participated in individual drawing sessions. Participants were directed to draw three different figures: a man, a woman, and themselves. Data analytic procedures involved assessment of the drawings using several different developmental checklists and charts, as well as Lowenfeld’s artistic stages of development, in order to give an estimate of the individual's mental age. This information was then compared to each participant’s Intelligent Quotient (IQ) score to determine whether the assessment of participant mental age based on Lowenfeld’s artistic stages of development matched with the individual’s mental age based on IQ score. The results for the study showed that HFDs created by adults with ID can provide the art therapist with the mental age of some individuals. Limitations of this study included small sample size, the age of the assessment tools used, and researcher bias. The information provided from this study may help provide art therapists with information pertaining to assessment of mental age in adults with ID, which may prove useful for future treatment planning and research.