Background: Durable operational tolerance after kidney transplantation remains uncommon. Most immunosuppression-withdrawal strategies have relied on calendar-based tapering rather than biologically informed decision-making. We tested whether biomarker-guided immunosuppression withdrawal could improve the safety and feasibility of minimization after living-donor kidney transplantation. Methods: This prospective, single-arm, open-label pilot study enrolled 22 adult, low-immunologic-risk recipients of primary living-donor kidney allografts between January 2021 and June 2022. All participants received induction with rabbit antithymocyte globulin and rituximab, followed by tacrolimus-, sirolimus-, and short-course mycophenolate-based maintenance without chronic corticosteroids. Withdrawal was initiated only after a predefined biomarker gate was satisfied, incorporating stable graft function, absence of donor-specific HLA antibodies, reassuring protocol histology, and a favorable composite immune-reconstitution profile. The primary endpoint was successful complete withdrawal of maintenance immunosuppression for 52 consecutive weeks without biopsy-proven acute rejection, donor-specific antibody development, recurrent disease, graft loss, death, or sustained graft dysfunction. Results: Fourteen of 22 recipients (63.6%) met biomarker eligibility for tacrolimus withdrawal at a median of 34 weeks (IQR 31–37) after transplantation, and 10 (45.5%) subsequently met eligibility for full withdrawal and discontinued all maintenance immunosuppression. Seven recipients (31.8%) met the primary endpoint. Overall biopsy-proven acute rejection occurred in 3 of 22 recipients (13.6%), all T cell-mediated; no antibody-mediated rejection occurred. De novo donor-specific HLA antibodies developed in 2 recipients (9.1%). There were no cases of patient death or graft loss. In exploratory analyses, recipients who met the primary endpoint showed higher transitional B-cell fractions (18.4% vs. 11.5%), higher naive-to-memory B-cell ratios (2.6 vs. 1.4), lower CD8+ TEMRA frequencies (21.7% vs. 31.9%), higher Treg/CD4 ratios (0.079 vs. 0.058), and lower serum BLyS concentrations (1.6 vs. 3.1 ng/mL) at the prewithdrawal biomarker assessment than recipients who failed to achieve durable withdrawal. Conclusions: In this pilot study, biomarker-guided immunosuppression withdrawal was associated with a subset of low-risk living-donor kidney transplant recipients in whom complete immunosuppression withdrawal appeared feasible with acceptable short-term safety. These hypothesis-generating findings support further prospective validation of immune-state-guided minimization strategies in larger cohorts.