This study aimed to assess the external and internal loads of Brazilian soccer referees during official matches. A total of 11 field referees (aged 36.2 ± 7.5 years) were monitored during 35 matches. The external (distance covered, mean and maximal speed) and internal load parameters (session ratings of perceived exertion [RPE] training load [TL], Edwards' TL, and time spent in different heart rate [HR] zones) were assessed in 3-4 matches per referee. External load parameters were measured using a wrist Global Positioning System (GPS) receiver. No differences in distance covered (5.219 ± 205 vs. 5.230 ± 237 m) and maximal speed (19.3 ± 1.0 vs. 19.4 ± 1.4 km·h^-1) were observed between the halves of the matches (p > 0.05). However, the mean speed was higher in the first half of the matches (6.6 ± 0.4 vs. 6.4 ± 0.3 km·h^-1) (p < 0.05) than in the second half. The mean HR during the matches was ~89% of HR_max. In ~95% of the matches, the referees demonstrated a HR ≥ 80% of HR_max. Nonetheless, the time spent at 90-100% of HR_max was higher in the first half (59.9 vs. 52.3%) (p < 0.05). Significant correlations between session RPE TL and distance covered at 90-100% of HR_max (r = 0.62) and session RPE TL and maximal speed (r = 0.54) (p < 0.05) were noted. Furthermore, there was a positive correlation between session RPE TL and Edwards' TL (r = 0.61) (p < 0.05). Brazilian soccer referees demonstrated high external and internal load demands during official matches. The portable GPS/HR monitors and session RPE method can provide relevant information regarding the magnitude of the physiological strain during official matches.

• High external and internal loads were imposed on Brazilian soccer referees during official matches.

• There was a high positive correlation between a subjective marker of internal load (session RPE) and parameters of external load (distance covered between 90-100% of HR and maximal speed).

• There was a high positive correlation between session RPE method and Edwards' method.

• Session RPE seems to be a reliable marker of internal load.

• The portable GPS/HR monitors and the session RPE method can provide relevant information regarding the magnitude of external and internal loads of soccer referees during official matches.