The aim of this study was to examine the concurrent validity of two portable systems for vertical jump (VJ) assessment under field conditions. VJ flight-time assessed using an optical mat (Optojump®) and an accelerometer-based (Myotest®) system were compared with a force-platform. The flight-time recorded during a countermovement jump were collected from 20 rugby players (n=86 jumps) concurrently using the three tracking systems. Significant bias between the Force-platform and either the Optojump® (bias=0.006±0.007; 95%CI 0.004 to 0.007s) and Myotest® (bias=-0.031±0.021; 95%CI 0.035 to -0.026s; p<0.0001) occurred. A nearly perfect correlation was found between force-platform and Optojump® (r=0.99; 95%CI 0.098 to 0.99; p<0.0001). Force-platform and Myotest® (r=0.89; 95%CI 0.084 to 0.93; p<0.0001) flight-times showed very large association. Difference between Optojump® and Myotest® systems was significant (-0.036±0.021s; 95%CI -0.041 to -0.032; p<0.0001), which results in Myotest® mean flight time being ∼7.2% longer than Optojump® flight-time. The association between Optojump® and Myotest® was nearly perfect (r=0.91, 95%CI 0.86 to 0.94; p<0.0001). This study showed that the Optojump® and Myotest® systems possess convergent validity and can be successfully used under field conditions to assess VJ while performing a countermovement jump. However caution should be exercised when interpreting data obtained from different portable systems for field measurement.