Dornhoefer was left unprotected in the 1967 NHL Expansion Draft. The Philadelphia Flyers selected him with the 13th pick overall, and he would never play with another team. . In that first year with Philadelphia, Dornhoefer scored 13 goals and 43 points while accumulating 134 penalty minutes and gaining a reputation as a hard hitting, grinding left winger with a touch for scoring. Two seasons later he reached the 20-goal plateau for the first time, a mark he would achieve in five seasons. In 1973 he had his best season, scoring 30 goals and 49 assists for 79 points and being named to play in the All-Star Game. The most famous play of his career came in the 1973 Stanley Cup playoffs when he scored a crucial overtime goal against the Minnesota North Stars on a solo rush. The goal was memorialized on a statue at the Spectrum, which was demolished in 2010-11. Plans are for the Spectrum statues to be installed in a new retail, restaurant and entertainment complex to be built on a nearby site. Although hampered by injuries throughout his career in consequence of his bruising style, Dornhoefer remained an effective scorer through his penultimate season, and was named to play in the All-Star Game again in 1977, and finished that regular season with a +47 plus/minus mark. The season thereafter, missing nearly half the season through injury, his scoring touch disappeared completely, and he retired after the 1978 playoffs. Dornhoefer played in 787 games over 14 seasons, scoring 214 goals and 328 assists for 542 points, adding 1291 penalty minutes. At the time of his retirement he was second only to Bobby Clarke as the team's all-time leading scorer, and still ranks tenth in that category. His eleven seasons with Philadelphia are surpassed only by Clarke, Bill Barber and Rick MacLeish, and on a team iconic for its brawling ways, Dornhoefer is eighth in franchise penalty minutes.
Post-playing career
After his retirement following the 1977–1978 season, Dornhoefer moved to broadcasting. He worked a short time in Philadelphia locally, then moved back to his native Ontario, Canada to work on Hockey Night In Canada as a color commentator from 1978–1987. After a six-year hiatus from broadcasting, Dornhoefer moved back to Philadelphia in 1992 and joined the Flyers broadcast team, originally working with play-by-play man Gene Hart. He served as a Flyers' color analyst through the 2005–06 NHL season. Dornhoefer became a citizen of the United States of America on March 16, 2016.
