Rationale & Objective: There is limited information about the association between primary kidney disease and donor relatedness with transplant outcomes. This study addresses this gap by evaluating clinical outcomes after kidney transplantation in recipients of living donor kidneys as a function of primary kidney disease type and donor relatedness in Australia and New Zealand. Study Design: Retrospective observational study. Setting & Participants: Kidney transplant recipients who received allografts from living donors between January 1, 1998, and December 31, 2018, as recorded in the Australian and New Zealand Dialysis and Transplant Registry (ANZDATA). Exposures: Primary kidney disease type categorized as majority monogenic, minority monogenic, or other primary kidney disease based on disease heritability as well as donor relatedness. Outcome: Primary kidney disease recurrence, graft failure. Analytical Approach: Kaplan-Meier analysis and Cox proportion hazards regression to generate hazard ratios for primary kidney disease recurrence, allograft failure, and mortality. Partial likelihood ratio test was used to examine possible interactions between primary kidney disease type and donor relatedness for both study outcomes. Results: Among 5,500 live donor kidney transplant recipients, majority monogenic (adjusted HR, 0.58, P < 0.001) and minority monogenic primary kidney diseases (adjusted HR, 0.64, P < 0.001) were associated with reduced primary kidney disease recurrence compared with other primary kidney diseases. Majority monogenic primary kidney disease was also associated with reduced allograft failure (adjusted HR, 0.86, P = 0.04) compared with other primary kidney diseases. Donor relatedness was not associated with primary kidney disease recurrence nor graft failure. No interaction was detected between primary kidney disease type and donor relatedness for either study outcome. Limitations: Potential misclassification of primary kidney disease type, incomplete ascertainment of primary kidney disease recurrence, unmeasured confounding. Conclusions: Monogenic primary kidney disease is associated with lower rates of primary kidney disease recurrence and allograft failure. Donor relatedness was not associated with allograft outcomes. These results may inform pretransplant counseling and live donor selection. Plain-Language Summary: There are theoretical concerns that live-donor kidney transplants may be associated with increased risks of kidney disease recurrence and transplant failure due to unmeasurable shared genetic factors between the donor and the recipient. This study analyzed data from the Australia and New Zealand Dialysis and Transplant (ANZDATA) registry and showed that, although disease type was associated with the risk of disease recurrence and transplant failure, donor relatedness did not impact transplant outcomes. These findings may inform pretransplant counseling and live donor selection.