Background <p>The clinical consequences and risk factors for posttransplant diabetes mellitus (PTDM) remain underexplored, particularly in the Pakistani population. This study aimed to assess the frequency of PTDM, identify its risk factors, and compare clinical outcomes with those of non-PTDM patients in a single center.</p> Methodology <p>A retrospective cohort observational study was conducted on 121 kidney transplant recipients aged 18 years or older from January 2018 to December 2021. Data were collected on demographic characteristics, pretransplant risk factors, and posttransplant outcomes at 3, 6, and 12 months. PTDM was diagnosed via international consensus guidelines, and clinical outcomes were compared between the PTDM and non-PTDM groups.</p> Results <p>Out of 492 transplant recipients, a total of 121 participants were included in the study; the mean age was 36.45 ± 10.56 years, the mean BMI was 27.65 ± 5.01&#xa0;kg/m², and the pretransplant mean FBS was 84.32 ± 12.22&#xa0;mg/dl. Predominantly, there were males (84.3%), mostly with hypertension as the primary diagnosis (86%). PTDM developed in 27.3% (<i>n</i> = 33) of the participants. PTDM patients had significantly higher fasting blood sugar (FBS) levels (<i>p</i> &lt; 0.0001) and worse outcomes, including higher rates of infection (27.27% vs. 3.41%, <i>p</i> &lt; 0.05), delayed graft function (15.15% vs. 0%, <i>p</i> &lt; 0.05), and transplant rejection (12.12% vs. 1.14%, <i>p</i> &lt; 0.05). Dyslipidemia was also more prevalent in the PTDM group than in the control group at 3, 6, and 12 months.</p> Conclusion <p>PTDM significantly impacts posttransplant outcomes, necessitating careful management to mitigate adverse events such as infection, graft dysfunction, and dyslipidemia. Early detection and targeted interventions may improve clinical outcomes in PTDM patients.</p> Clinical trial number <p>Not applicable.</p>