Emerging sea cucumber (Cucumaria frondosa) fisheries have recently developed off the coast of Atlantic Canada. The reproductive cycle, developmental stages, and feeding biology of this species have been described, but fishery-related metrics remain largely unknown. Measuring lengths and weights of individuals in fished populations is fundamental for stock assessment and management. These measurements are used to identify trends in individual size related to fishing pressure on the population over time. Length and weight measurements are recorded for commercially caught C. frondosa, but plasticity of their body makes precise measures difficult, resulting in varying techniques that lack consistency. Several methods of measuring and estimating size and weight of C. frondosa were tested for accuracy in a laboratory setting. Indices that accounted for the size of individuals on multiple planes proved more useful for estimating wet weight than length or width alone. Accurate wet weight estimates were possible from drop-camera images taken of individuals in situ using size indices that combined length and width, as well as area covered. Timing of measurements was a key variable. The time out of water significantly changed the wet weight measurements, with an average weight change of 31.93% (SD ± 14.92) over a 1-h period, but after the first 10 min, measures were consistent, suggesting animals expelled most of their fluid shortly after removal from the water. Although there are many sources of potential error when measuring C. frondosa, consistent timing and size metrics that incorporate overall size, as opposed to a single dimension, show promise for evaluating changes in individual size over time. Standardized methods will enable the collection of data that can be used in stock assessment to determine reference points and vital statistics for this developing fishery.