Recovery of walking after incomplete spinal cord injury (iSCI) is a common focus of rehabilitation, but few measurement tools capture walking performance outside the clinic or laboratory. This study determined the accuracy and test-retest reliability of the Step Activity Monitor (SAM), a microprocessor-driven accelerometer that measures walking activity. We evaluated 11 individuals with iSCI during replicate 6-minute walk tests (6MWTs) and 10-meter walk tests (10mWTs) scheduled <1 week apart. The SAM was 97% accurate compared with hand-tallied step counts. SAM values were stable across repeated walking performances (intraclass correlation coefficient = 0.97-0.99). Standard error of measurement values were 6.0 steps and 0.8 steps for the 6MWT and 10mWT, respectively. Ninety-five percent confidence intervals were 203.7 to 177.0 steps for the 6MWT and 16.1 to 12.7 steps for the 10mWT. The SAM is an accurate and reliable device for capturing walking activity in individuals with iSCI.