He has beaten golden-generation players from Argentinian tennis such as Gastón Gaudio, Guillermo Cañas, Mariano Puerta, Juan Martin del Potro, and David Nalbandian. 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.