Methionine (Met) is typically the first limiting amino acid (AA) in practical shrimp diets. T o precisely meet this requirement, supplemental Met sources are routinely used. More recently , a dipeptide of DL-Met (DL-Methionyl-DL-Methionine) or 'Met-Met' in short (AQUAVI® Met-Met , Evonik Nutrition & Care, GmbH, Germany ) was specifically developed for shrimps . Previous studies have shown that Met-Met is the most effective Met source for shrimps attributed mainly to (i ) its minimal water solubility and leaching and (ii) slower and longer release of Met from its different stereoisomers (DL-, LD-, LL-, and DD-Met-Met), providing opportunity for better synchronicity of Met with the AA released from intact protein sources. Previous in-vitro studies with enzymes extracted from shrimp hepatopancreas showed that shrimps are able to completely cleave the 4 isomers of Met-Met but at different rates, allowing for delayed liberation and absorption of D- and L-Met in the digestive tract. However, limited in-vivo data have been published showing changes in the postprandial profile of Met in the hemolymph of shrimp fed different Met sources. Two trials were conducted to determine the postprandial Met levels in relation to other AA in the hemolymph of whiteleg shrimp fed diets with supplemental Met-Met or D L-Met at a feeding frequency of once per day (Trial 1; initial BW = 17g ) or three times per day (Trial 2; initial BW = 21g). In both trials, a b asal diet was formulated to contain ~37% CP , 8% lipid, ~20 MJ/kg gross energy and to meet or exceed the nutritional requirements with the exception of Met. Two test diets were formulated by replacing 0.30% glycine from the basal diet with 0.30% DL-Met (DL-Met diet) or 0.31% Met-Met (Met-Met diet). Diets were pressure pelleted using a meat grinder and a 3- mm die and dried to a moisture content of 8-10% and stored at 4 °C. Analyzed Met and other AA levels were in agreement with formulated values. Shrimps were preconditioned to the experimental diets at one feeding per day (Trial 1) or 3 times per day (Trial 2) 4 days before hemolymph sampling. In each trial, 54 tanks with 4 shrimps per tank (80 l volume) were used. Shrimp fed with the Met-Met diet exhibited significantly greater Met levels (as % of total AA ) in the hemolymph than those fed with the basal or the DL-Met diets. Within 15 min of feeding, an upswing of Met and total AA in the hemolymph was apparent showing very quick processing and digestion of nutrients. The clearance of AA was also relatively fast with AA levels returning to the basal fasting levels at 60-120 min post feeding at 1x feeding. Similar response was also observed at 3x feeding where it was tracked up to 60 min post- feeding. Feeding shrimp 3 times a day resulted in greater Met level in the hemolymph than those fed 1 time a day, but the advantage of feeding Met-Met was not affected . Overall, data suggest that feeding shrimp with the Met-Met diet compared with the DL-Met diet results in higher Met levels in the hemolymph over time and therefore, supplemental Met-Met can support for higher body protein synthesis relative to DL-Met. This in-vivo study provides evidences for the higher biological efficiency observed in the previous studies for supplemental Met-Met.