Born in Slatina, Romania, Ionel Dănciulescu started playing football in his hometown as a youngster for CSŞ Slatina, and was said to have great potential for striking a ball and to score goals. In his early career he got noticed immediately and was transferred in the capital of his region, Oltenia at Electroputere Craiova.
In 1993, Dănciulescue joined Electroputere making his Divizia A debut on 6 October 1993 against the derby rival at that time Universitatea Craiova, which ended 2–2. Over the course of two seasons with Electroputere, he scored 8 goals in 31 league games playing alongside the likes of Ștefan Nanu, Gabriel Popescu, and two other (later team-mates at Steaua), Sabin Ilie and Claudiu Răducanu. In 1995, Electroputere Craiova were relegated to the second league. Dănciulescu signed for Dinamo Bucharest and went on to become a promising striker.
Having arrived in 1995, Dănciulescu only spent two seasons at Dinamo București, scoring 22 goals in 64 games. However, he did not win any trophies with Dinamo. He left the club for Turkey in 1997.
During the half season of 1997–98, Dănciulescu had a brief spell with Altay in the Turkish Super League. He played there seven games and scoring one goal.
After returning from Turkey, Dănciulescu decided to join Romanian team Steaua București. He played three seasons with Steaua, scoring 54 goals in 129 league games. In the seasons 1997–98 and 2000–01 Steaua won the championship titles as well as the Romanian Cup in 1998–99 and a Romanian Supercup title in 2001.
In the second part of the season 2001–02 Dănciulescu had a conflict with both Gigi Becali, the boss of Steaua București, and Victor Pițurcă, Steaua's coach, and had to leave along with Ion Vlădoiu.
He signed again with Dinamo Bucharest, but his second spell period was probably the hardest in his career. He even played in the second league at that time via Dinamo's satellite team Poiana Câmpina. He came back strong during the 2002–03 season, after he scored 16 goals in 26 games. The fans accepted him and he became the top-scorer of the team along with Claudiu Niculescu. The Romanian press called them the "N&D couple".
In 2004, he was named Romanian Footballer of the Year, after becoming the top goalscorer in the 2003–04 season of Divizia A and scoring 2 goals in 5 matches with the national team. During his second spell with Dinamo, Dănciulescu won the Romanian League in the seasons 2003–04 and 2006–07, and two more Romanian Cups in 2002–03 and 2003–04. As of August 2008 he was the fourth overall goalscorer in the history of the Romanian First Division (with 187 goals), after Dudu Georgescu, Rodion Cămătaru and Marin Radu. He was top scorer in the 2007–08 season, scoring 21 goals for Dinamo Bucharest, which he also captained several times that season.
In 2005, he was loaned out to China side Shandong Luneng, which paid him 350.000 USD for 10 months. Dănciulescu scored 10 goals in 25 league games being the top-scorer of the team and helping them to reach the Chinese FA Cup final, where they finished runners-up.
On 1 September 2009, Dănciulescu signed for Spanish side Hércules Alicante in the Segunda División securing a two-year deal. On 19 June 2010, Dănciulescu helped Hércules to promote to La Liga, after a break of 13 years, contributing 10 goals in 25 league games. He also scored two goals in the Spanish Cup against SD Huesca and Almería and became the overall top scorer of the team.
After only one year with Hércules, his contract was terminated so Dănciulescu came back to Dinamo in July 2010. He became a regular player for Dinamo in Ioan Andone's coaching spell and remained in the first squad in 2011, with Liviu Ciobotariu as manager. On 26 September 2011, he scored his 198th goal in Liga I in a match against Petrolul Ploiești, thus joining Rodion Cămătaru as the second most prolific goalscorer. On 17 October, Ionel Dănciulescu scored his 200th goal in Liga I, during a match against Ceahlăul Piatra-Neamț.
In September 2013, Dănciulescu became the most prolific goalscorer in Cupa României after he scored once in a game against Sănătatea Cluj. He reached 41 goals in the competition, passing the record of Florea Voinea.
As of 6 October 2013
Dănciulescu won his first Romania cap on 3 March 1999 against Estonia, in a 2–0 victory. However he was never in the plans of Victor Pițurcă, the man who brought him on the national team first time against Estonia, and was never called up again, due to the dispute he had with Pițurcă when he was at Steaua. Dănciulescu was once called up during 2004 and 2009 by Anghel Iordănescu and Răzvan Lucescu.
He played only eight games for Romania, his best match was a friendly one against Germany ended with Romania's victory, 5–1 when he scored his only two goals for Romania.Romania's goal tally first. "Score" column indicates the score after the player's goal.
Liga 1: 1997–98, 2000–01
Romanian Cup: 1998–99
Romanian Super Cup: 2000–01
Liga 1: 2001–02, 2003–04, 2006–07
Romanian Cup: 2002–03, 2003–04, 2011–12
Romanian Supercup: 2005, 2012
Chinese FA Cup: Runner-up: 2005
Liga 1 Golden Boot: 2003–04, 2007–08
Romanian Footballer of the Year: 2004