In October 2003, at age 15, Giraldo became the youngest player in his country to be ranked by the ATP, getting his first point with the
ITF Futures tournament in Medellín. In 2005, he won his first professional tournament in Medellín, and a 15,000 dollar prize, in the ITF Futures category. In 2006, age 18, he won the Challenger de Bogotá title and reached the Challenger de Medellín final. In March 2007, Giraldo won the Challenger de Bogotá title, beating the Brazilian
Flávio Saretta, and won the Challenger de Quite against
Giovanni Lapentti. He reached two finals in the same Challenger category. Although he lost to the Spanish Fernando Vicente in the Challenger de San Luis Potosí, he was close to the Top-100, reaching position 115, and also entered the
Roland Garros' main draw as a "lucky loser". In October of the same year, he reached the Challenger de Bogotá final, losing to
Marcos Daniel. His only ATP triumph in 2007 was beating the Venezuelan
Yohny Romero in the Davis Cup, helping Colombia win the series, 3–1, against Venezuela. During 2008, Giraldo had a 19–17 record in Challenger tournaments, he made it to the final at Challenger de Furth's final, losing to
Daniel Köllerer, and to Challenger de Cali's semifinals. He made it to final draws five times, including the
ATP World Tour Masters 1000 tournaments at
Indian Wells and
Miami. For the second consecutive year, he made
Roland Garros' main draw, losing in the first round to
Florent Serra. Giraldo opened 2009 by winning the Challenger de Salinas title, defeating Michael Rusell in the final, and, in March, had his sole triumph at the ATP level in the Davis Cup match versus Uruguay. Giraldo then qualified for the Indian Wells-Masters 1000's main draw and lost in the first round to
Nicolás Lapentti. One month later, Giraldo won the Challenger de San Luis Potosí's title against the Italian
Paolo Lorenzi. For the third consecutive year, Giraldo entered the Roland Garros' main draw, losing to
Denis Istomin in five sets in the first round. In the final stretch of the season, Giraldo won 19 out of 26 matches, reaching the Challenger de Cali and Quito semifinals and winning the Sacramento title (defeating Canadian
Jesse Levine in the finals) but losing again to Nicolás Lapentti in Guayaquil's final. Giraldo qualified for the
Australian Open main draw for the first time by virtue of his previous results. He won US$96,412 during 2009 and finished his best year out of the top-100 (105), with three Challenger titles and a 38–14 record. At the
2010 Australian Open, Giraldo beat off-seed No. 16
Tommy Robredo (6–4, 6–2, 6–2) in the first round. However, he lost in the second round to
Łukasz Kubot (4–6, 6–3, 3–6, 1–6). At the
2010 Internazionali BNL d'Italia in Rome, a Masters 1000 event, he produced a heavy ground game to crush 12th seed Juan Carlos Ferrero (6–0, 6–3) in the first round, followed by a 6–3, 6–2 win over
Michaël Llodra in the second round. However his run was ended at the hands of World No. 10 and 7th seed
Jo-Wilfried Tsonga (3–6, 4–6) in the third round. At the
2011 Heineken Open in Auckland, New Zealand, Giraldo made it to the semi-finals, where he lost to
David Ferrer (3–6, 5–7). At the
2011 Australian Open, he reached the second round where he lost to
Marin Čilić (3–6, 6–7, 1–6). He reached the final of the 2011
Movistar Open where he lost to
Tommy Robredo (2–6, 6–2, 6–7) despite serving for the championship at 5–3. At the
2011 US Open, Giraldo drew World No. 3
Roger Federer in the first round, to whom he lost in straight sets (4–6, 3–6, 2–6). At the
2013 French Open Giraldo lost in the first round to
Grega Žemlja (4–6, 1–6, 4–6). In the first round of
2014 Heineken Open, Giraldo beat Spaniard
Albert Montañés in straight sets (6–1, 7–6). His tournament ended in the second round, losing in a 3-setter against
Guillermo García López (7–6(7), 2–6, 3–6). He beat
Marcel Granollers and Guillermo García López at Viña del Mar to reach the semi-finals, where he was defeated by
Leonardo Mayer. He upset
Tommy Robredo at the
2014 U.S. Men's Clay Court Championships and reached the semi-finals, where he lost to
Fernando Verdasco. At the
2014 Barcelona Open Banc Sabadell, he reached his second ATP final, and the first one in an
ATP World Tour 500 series tournament. On the way, he defeated 3rd-seeded
Fabio Fognini, 10th-seeded
Philipp Kohlschreiber and 6th-seeded
Nicolás Almagro. He lost the tournament against
Kei Nishikori in straight sets (2–6, 2–6). In May 2014, in the second round of the
2014 Mutua Madrid Open Giraldo beat 11th-seeded Frenchman
Jo-Wilfried Tsonga in straight sets (6–4, 6–3). Then he achieved his first win against a top-10 player, defeating the World No. 8 and two-time Grand Slam champion
Andy Murray in straight sets (6–3, 6–2). He advanced to the quarterfinals but lost to
Roberto Bautista Agut. At
the 2014 Wimbledon tournament, Giraldo defeated
Marcel Granollers in the second round and lost to
Roger Federer in the third round. At
Washington he was defeated by
Vasek Pospisil in the quarter-finals. At the
US Open he was beaten by
Teymuraz Gabashvili in the first round. He reached the semi-finals at
Shenzhen, where he lost to
Tommy Robredo. In 2016, Giraldo lost to 32nd-seed
João Sousa in the second round of the
2016 Australian Open. Giraldo lost in the first round of the
2016 French Open. Giraldo lost in the first round of
2016 Wimbledon Championships to
Gilles Müller, in a match that went to 5 sets, Muller eventually prevailing, 15–13, in the last set. Giraldo won the
Advantage Cars Prague Open, which included an impressive win in the quarter-finals against world number-26
Martin Kližan. Giraldo entered the new
2016 Los Cabos Open tournament. He beat
Amir Weintraub in straight sets, then faced 4th seed
Sam Querrey, whom he defeated in straight sets. He lost to wild-card
Pablo Carreño Busta in the quarterfinals. ==Playing style==