The rookie outfielder led off the game with his second homer of the season before belting another long ball in the bottom of the second inning at Great American Ball Park in Cincinnati.
Senzel, 23, hit his first career home run in the Reds' 9-2 win agains the Giants on Saturday in Cincinnati.
Both of his bombs on Monday came against Giants starter Drew Pomeranz. Senzel stepped into the box for his first shot and took a ball from the left-hander. Pomeranz then tossed in an 89.7-mph fastball. Senzel squared up the offering and sent the baseball flying over the right center field fence.
The solo shot had an exit velocity of 100 mph and an estimated distance of 369 feet, according to Statcast.
Joey Votto singled in the next at-bat, before coming in to score on a Eugenio Suarez homer. Jose Iglesias plated Kyler Farmer with an RBI triple before Curt Casali brought in Cincinnati's fifth run of the inning with an RBI single.
Senzel's next bomb had an estimated distance of 350 feet and an exit velocity of 99 mph. It was also of the leadoff variety. Senzel settled in against Pomeranz once again in the second frame. He worked to a 1-1 count after taking two knuckle curveballs from the lefty. He belted Pomeranz's third offering over the right field fence, giving the Reds a 6-1 edge.
Jose Iglesias later gave the Reds a 7-1 lead with an RBI double in the same inning.
Senzel's hot streak ended in the third frame when he was struck out by Giants reliever Nick Vincent. Cincinnati led 7-1 after four innings.
Senzel is now hitting .286 with three home runs, three RBIs, four runs scored and four walks for Cincinnati.
The Reds travel for a three-game series against the Oakland Athletics, starting at 10:07 p.m. on Tuesday in Oakland. Cincinnati gets another matchup against the Giants following the Oakland series.