Weight category athletes are known for practicing rapid weight loss before competition weigh-in. After weigh-in, athletes strive to restore euhydration and body mass through food and fluid intake. The aim of the current study was to assess prevalence of hypohydration at competition time among elite athletes' in four different combat sports, and how water intake and timing of official weigh-in were related to hydration status. Participants were 31 taekwondo practitioners and wrestlers who performed evening weigh-in (EWI) the night before competition day and had thus time for rehydration, and 32 boxers and judokas conducting competition day morning weigh-in (MWI). In total, 32% were female. Urine specific gravity (USG) was measured by refractometry on the competition day's first morning urine sample. Hypohydration was defined as USG ≥ 1.020 and serious hypohydration as USG > 1.030. Water intake was measured by means of dietary records. The prevalence of hypohydration was 89% in the morning of competition day. Serious hypohydration was also prevalent. This was found in over 50% of MWI athletes and in 42% of the EWI group. A higher water intake, from both fluids and solid foods, in the evening before competition day was not associated with a more favorable hydration status the following morning. In conclusion, neither weigh-in close to competition nor evening weigh-in with more time for rehydration seems to prevent hypohydration before competition.