Raley (1-2), a 24-year-old former sixth-round draft choice by the Cubs out of Texas A&M University, scored his first victory in his third big-league start.
The left-hander went 5 1/3 innings, yielding four runs (three earned) on five hits, walking two and striking out four as Chicago earned a split in a day-night double-header.
Cincinnati won the first contest 7-3.
Carlos Marmol was called on to make his 15th save after Chicago's bullpen surrendered three late runs.
Starlin Castro went 3-for-5 with two RBI and rookie first-round draft pick Brett Johnson socked his first major-league homer to highlight the Cubs' 13-hit attack.
Todd Redmond (0-1), called up by the Reds from Class AAA Louisville before the game, was touched for four runs on seven hits over 3 1/3 innings in his major-league debut.
Ryan Ludwick belted two homers for National League Central-leading Cincinnati.