Ranger was selected in the second round of 2000 OHL Draft by the Oshawa Generals, for whom he played parts of four seasons in the Ontario Hockey League. The Whitby, ON native missed most of his rookie season for Oshawa due to a broken wrist. At the end of his second season, Ranger opted into the 2002 Entry Draft despite posting 0 goals and just 10 assists to that point in his junior career. That year Ranger was selected to play in the CHL Top Prospects game in Saskatoon and was later selected by the Tampa Bay Lightning in the 6th round of the NHL Entry Draft.
By the time Ranger attended his first rookie camp for the Tampa Bay Lightning in August of 2002 he was still just 17 years old making him by far the youngest Lightning prospect attending the camp. He did not, however, look out of place amongst his older peers and returned to the OHL poised for a breakout season. In 2002-2003 Paul Ranger had 10 goals and 38 points in 68 games and made a reputation for himself as one of the most mobile and offensively aggressive defensemen in the OHL. In his final campaign in 2003-2004, Ranger set career highs with 12 goals and 43 points and was nominated by Oshawa for the Max Kaminsky Trophy for the best defenseman in the Ontario Hockey League. He also represented the Western Conference in the 2004 OHL All-Star Game. In the summer of 2004, Ranger was signed to a standard three year entry level contract by the Tampa Bay Lightning.
Ranger began his professional career with the Springfield Falcons of the AHL under the pall of the NHL Lockout. While at times struggling to adjust to the professional ranks early in the season, Ranger began to hit his stride the final quarter of the season. In his final 12 games of the season, Ranger scored 6 of his 11 points for the season and was a team leading +8 over that span. The next fall, with labor peace established, Ranger attended his second full Lightning training camp and finished second in scoring amongst all Lightning defensemen in intrasquad scrimmages behind only Dan Boyle with 5 points in 5 scrimmage games. After a poor exhibition outing in Montreal, however, Ranger was returned to Springfield on 9/21/05.
Ranger's stint in Springfield would be a short one however. In two preseason games with the Falcons Ranger registered 1 goal and 2 assists including the overtime game winning goal in the preseason finale against the Hartford Wolfpack. Then, in the season opener, Ranger potted the game winning goal and 2 assists in a 4-2 victory over the Portland Pirates. At the recommendation of Springfield head coach Dirk Graham, the Tampa Bay Lightning recalled Paul Ranger on 10-14-05. The next day, Ranger made his debut against the Pittsburgh Penguins in a 3-1 Lightning victory.