2010-11: Connor Chatham attended USA Hockey's Select 15 Development camp in July 2010 and appeared in twelve games for the St. Louis Junior Blues midget AAA team; missing much of the year due to shoulder surgery. He scored 2 goals with 2 penalty minutes. In March 2011 he committed to skating in USA Hockey's National Team Development Program for the 2011-12 season. Chatham was selected by Plymouth in the fifth round (88th overall) of the 2011 OHL Priority Draft.
2011-12: Chatham skated in 56 games for the US NTDP's U17 team in his first season in Ann Arbor and skated for the USA's silver-medal winning U17 squad at the 2012 World Hockey Challenge in Canada. He scored 7 goals with 13 assists and had 45 penalty minutes in the regular season. In five games at the WHC he scored 1 goal with 1 assist and had 4 penalty minutes. Chatham committed to playing college hockey at the University of Denver in July 2011 and was selected by Omaha in the third round (39th overall) of the 2012 USHL Entry Draft.
2012-13: Chatham left the NDTP to skate for Omaha in the USHL; appearing in 63 games for the Lancers. He was the team's third leading scorer with 18 goals and 17 assists and was -12 with 71 penalty minutes. Omaha finished fifth in the Western Conference; missing the USHL playoffs. In July 2013 he signed with the OHL's Whalers; opting out of his commitment to Denver.
2013-14: Chatham was one of several first-year OHL players to join defending West Division champion Plymouth. Showing steady progress skating for the rebuilt Whalers he scored 8 goals with 10 assists and was -19 with 37 penalty minutes in his first 39 games; missing time in October due to a hand injury. Chatham skated in the 2013 USA Hockey CCM All-American Prospects game in September and was ranked 30th amongst North American skaters in Central Scouting's mid-term rankings prior to the 2014 NHL Draft.