Approximately 40% of the kidneys for transplant worldwide come from living donors. Despite advantages of living donor transplants, rates have stagnated in recent years. One possible barrier may be costs related to the transplant process that potential willing donors may incur for travel, parking, accommodation, and lost productivity.To better understand and quantify the financial costs incurred by living kidney donors, we conducted a prospective cohort study, recruiting 912 living kidney donors from 12 transplant centers across Canada between 2009 and 2014; 821 of them completed all or a portion of the costing survey. We report microcosted total, out-of-pocket, and lost productivity costs (in 2016 Canadian dollars) for living kidney donors from donor evaluation start to 3 months after donation. We examined costs according to () the donor's relationship with their recipient, including spousal (donation to a partner), emotionally related nonspousal (friend, step-parent, in law), or genetically related; and () donation type (directed, paired kidney, or nondirected).Living kidney donors incurred a median (75th percentile) of $1254 ($2589) in out-of-pocket costs and $0 ($1908) in lost productivity costs. On average, total costs were $2226 higher in spousal compared with emotionally related nonspousal donors (=0.02) and $1664 higher in directed donors compared with nondirected donors (<0.001). Total costs (out-of-pocket and lost productivity) exceeded $5500 for 205 (25%) donors.Our results can be used to inform strategies to minimize the financial burden of living donation, which may help improve the donation experience and increase the number of living donor kidney transplants.