Glycine transporter type‐1 (GlyT1) has been proposed as a target for drug development for schizophrenia. PET imaging with a GlyT1 specific radiotracer will allow for the measurement of target occupancy of GlyT1 inhibitors, and for in vivo investigation of GlyT1 alterations in schizophrenia. We conducted a comparative evaluation of two GlyT1 radiotracers, [11C]GSK931145, and [18F]MK‐6577, in baboons. Two baboons were imaged with [11C]GSK931145 and [18F]MK‐6577. Blocking studies with GSK931145 (0.3 or 0.2 mg/kg) were conducted to determine the level of tracer specific binding. [11C]GSK931145 and [18F]MK‐6577 were synthesized in good yield and high specific activity. Moderately fast metabolism was observed for both tracers, with ∼30% of parent at 30 min post‐injection. In the brain, both radiotracers showed good uptake and distribution profiles consistent with regional GlyT1 densities. [18F]MK‐6577 displayed higher uptake and faster kinetics than [11C]GSK931145. Time activity curves were well described by the two‐tissue compartment model. Regional volume of distribution (VT) values were higher for [18F]MK‐6577 than [11C]GSK931145. Pretreatment with GSK931145 reduced tracer uptake to a homogeneous level throughout the brain, indicating in vivo binding specificity and lack of a reference region for both radiotracers. Linear regression analysis of VT estimates between tracers indicated higher specific binding for [18F]MK‐6577 than [11C]GSK931145, consistent with higher regional binding potential (BPND) values of [18F]MK‐6577 calculated using VT from the baseline scans and non‐displaceable distribution volume (VND) derived from blocking studies. [18F]MK‐6577 appears to be a superior radiotracer with higher brain uptake, faster kinetics, and higher specific binding signals than [11C]GSK931145. Synapse 70:112–120, 2016. © 2016 Wiley Periodicals, Inc.