Objective To investigate anxiety- and depression-like behaviors in Cynomolgus monkeys with type 2 diabetes mellitus ( T2DM ), and to explore their correlations with biochemical parameters. Methods Cynomolgus monkeys were divided into a T2DM group (fasting plasma glucose (FPG) ≥ 5. 6 mmol / L) and control group (FPG < 4. 2 mmol / L) ( n = 3 per group). Age, sex, body mass, body mass index( BMI), FPG, blood lipids, atherosclerosis index ( AI), and tumor necrosis factor-α ( TNF-α) levels were measured in both groups. Anxiety-like behaviors were assessed using the human intrude test ( HIT) and depression-like behaviors were evaluated using the apathy feeding test ( AFT). Relationships between behavioral parameters and biochemical /inflammatory markers were evaluated using Pearson’ s correlation analysis. Results ( 1) FPG, AI, and TNF-αlevels were significantly elevated while high-density lipoprotein cholesterol levels were reduced in the T2DM group compared with the control group (P<0. 05). (2) Regarding the HIT result, the durations of anxious (stare phase) and back-of-cage (stare phase) behaviors were higher in the T2DM group than in the control group (P<0. 05), while the durations of locomotor behaviors (baseline phase, profile phase, back phase) were significantly shorter (P<0. 05). ( 3) The AFT revealed that food retrieval latency was significantly delayed in the T2DM group ( P<0. 05). Pearson’s analysis identified a positive correlation between back-of-cage (stare phase) duration and AI (r=0. 828, p= 0. 042), while locomotion during the back phase showed a negative correlation with AI (r= -0. 842, p= 0. 035). Conclusions Cynomolgus monkeys with T2DM display distinct anxiety- and depression-like behavioral phenotypes, with a significant association between the AI and anxiety-related behaviors. These findings provide novel insights into the pathophysiological mechanisms linking T2DM with neuropsychiatric comorbidities.