The main objective was to investigate the intra- and intertester reliability of a simple screening tool assessing errors in exercise execution by visual observation. 38 participants with no previous resistance exercise experience practiced for two weeks four typical upper limb exercises using elastic tubing. At 2-week follow-up, the participants were invited for a test-retest assessment on errors in technical execution. The assessment was based on ordinal deviation of joint position from neutral of the shoulder, elbow, and wrist in a single plane by visual observation. Moderate intratester reliability weighted kappa (w kappa) score ranging from 0.50 (0.21-0.71) to 0.57 (0.24-0.82) for observer 1 and a fair to moderate intratester reliability w kappa score ranging from 0.27 (0.09-0.43) to 0.52 (0.15-0.86) for observer 2 across the four exercises was observed. For intertester reliability moderate to substantial mean w. scores were found between the two observers, slightly improving from round one to round two ranging from 0.40 (0.20-0.59) to 0.68 (0.45-0.91) in round one to 0.52 (0.20-0.80) to 0.69 (0.39-0.86) in round two. The exercise error assessment demonstrated fair to substantial intratester and intertester reliability, which is congruent with previously published studies. Hence the simplicity of defining a neutral joint position for each of the involved joints in the exercise and categorizing the deviation in "some deviation" and "substantial deviation" to either side in a single plane is a viable and inexpensive solution when assessing for errors during exercise.