Heralded by some as the greatest goalie to ever play the game, Kappler showed his prowess in both college and club lacrosse. After attending Baltimore Polytechnic Institute in 1952, Kappler played for the Mt. Washington Lacrosse Club in 1953. He then went on to the University of Maryland where he played on the freshman team in 1954. He was selected to the All-American second team in his first varsity year (1955), and was accorded first team All-America honors in his junior and senior years.
Jimmy helped lead Maryland to national championships his sophomore and junior years. Perhaps the highest collegiate honor bestowed on Kappler was the C. Markland Kelly Award, honoring him as the outstanding goalie in the state of Maryland during all three of his varsity years. In his senior year he won the Charles P. McCormick Award, the Cone Award, and was the recipient of the Maryland Ring, the highest athletic award at the University of Maryland.
After graduating from Maryland he was a member of the 1957 South All-Star Team and was picked every year to the Club All-Star team from 1960 through 1967. As a result of his outstanding play during his ten years at the Mt. Washington Club he was placed on the Mt. Washington Club Honor Roll. Jimmy played in the 1967 World Games in Canada where his Mt. Washington team represented the U.S. and won the World Championship.
Kappler was inducted into the University of Maryland's Lacrosse Hall of Fame in 1975, and into their Athletics Hall of Fame in 1986. He was also selected to the ACC 50th Anniversary Men's Lacrosse Team in 2002. He was inducted into the Maryland State Athletic Hall of Fame in 2012, and in 2013, was selected to the Maryland State Athletic Hall of Fame Board of Directors.