[1][2] His mother, Lorene, worked at an aerospace parts company in Santa Ana and helped Klesko learn to play baseball.

She enrolled him in pitching school with Ron Lefebvre and put on catcher's gear herself to catch Klesko three times a week.

[2] Klesko attended Westminster High School, where even though he hit a lot of home runs, he starred as a pitcher, throwing a ninety-two mile per hour fastball and pitching for the USA Junior Olympic team.

His .525 slugging percentage as a Brave ranks fourth all-time among the team's career leaders, ahead of Eddie Mathews.

[11] Klesko and fellow former Atlanta Braves pitcher John Smoltz were named in a tax dispute involving conservation easement for a 1,546-acre non-cash donation the two made on behalf of a partnership the two formed in the early 1990s.

[12] On 25 April 2024, the court cleared the two of fraud charges, but reduced the assessed value of the donated easement to one-tenth of the claimed amount, and imposed a 40% penalty.