With Ascoli, he was ensured a starting spot in the lineup during the 2005–06 season, scoring his first goal in Serie A on 21 December 2005, a 1–0 home win over Treviso.

However, Udinese immediately sold half of his registration rights to newly promoted Ascoli as part of a co-ownership deal.

He stayed at Ascoli for just one season, scoring just three times in 33 appearances, and his rights were bought back in full by Udinese in June 2006 for an undisclosed fee.

His breakout season at Sampdoria led to a call-up to the Italy national team and numerous rumors of a high-profile transfer abroad.

[8] Following his breakout 2006–07 season, both Udinese and Sampdoria were unable to comes to terms on his co-ownership deal and went to a blind auction on 21 June 2007.

However, he soon found his footing at the club, forming a dangerous strike partnership with Antonio Di Natale and scoring a total of 12 goals in the 2007–08 season.

On 1 June 2009, Quagliarella moved to his hometown club Napoli for a transfer fee of €18 million, where he signed a five-year deal.

He was an unused bench in the second leg, which Walter Mazzarri used new signing Edinson Cavani partnered with Lavezzi, who the former scored a brace to help the team qualify.

Quagliarella opened the scoring in the March 2013 Derby d'Italia game against Inter Milan with a curled shot from 25 yards (23 m), and made the pass for Alessandro Matri's winner.

In his first Serie A match back at the club, he won a penalty after being fouled by Inter's Nemanja Vidić, but Marcelo Larrondo missed it and the game finished goalless.

[18] After a series of controversies with Torino's fans,[19] resulting from Quagliarella's failure to celebrate after a goal scored against his former club Napoli,[20] on 1 February 2016 he was loaned to Sampdoria with an obligation to buy.

During the 2018–19 Serie A season, on 2 September 2018, Quagliarella scored the final goal of a 3–0 home win against Napoli, with what was described by the BBC as a "sensational" backheel volley.

[39] On 5 March 2023, Quagliarella made his 550th appearance in Serie A against Salernitana, thus becoming the fifth outfield player to achieve this feat, following Pietro Vierchowod, Javier Zanetti, Francesco Totti and Paolo Maldini.

[47] Following his impressive performances with Sampdoria in the 2006–07 season, Quagliarella was called up to the Italian senior squad, known as the Azzurri, for a friendly against Romania in February 2007.

[48][49] In Kaunas on 6 June 2007, he made his first start for Italy in a vital Euro 2008 qualifier against Lithuania, also scoring his first two goals for the national side in the eventual 2–0 win.

Quagliarella was subsequently included in the Italian UEFA Euro 2008 squad by manager Roberto Donadoni;[52] he made his only appearance of the tournament in Italy's second group match, a 1–1 draw against Romania, coming on as a second-half substitute for Alessandro Del Piero.

[59] In Italy's final match of Group F at the 2010 World Cup against Slovakia, Quagliarella came on at the beginning of the second half for Gennaro Gattuso, with Italy trailing 1–0, and in the space of 45 minutes, he contributed to teammate Antonio Di Natale's goal, who scored from a rebound, and subsequently executed a beautiful 25-yard chip in injury time to bring the score to 3–2; furthermore, throughout the match, he also had a volley cleared off the line by Slovak defender Martin Škrtel, and had an equalising goal controversially ruled offside, although he was ultimately unable to prevent the Italians from losing 3–2, resulting in one of Italy's most shocking World Cup eliminations.

[68] On 23 March 2019, Quagliarella came off the bench in the 80th minute for Italy, in a 2–0 home win over Finland; this was 3,048 days since his last appearance, which had come in November 2010.

[69] On 26 March, Quagliarella was handed his first international start since 5 June 2010, and his first competitive start since 14 October 2009 (a 3–2 home victory over Cyprus in a 2010 World Cup qualifier, which was also held at the Stadio Ennio Tardini in Parma), scoring twice from the penalty spot in a 6–0 home win over Liechtenstein to become Italy's all-time oldest goalscorer, at the age of 36 years and 54 days; he also set-up Moise Kean's goal during the match.

[76] Although not a renowned sprinter, Quagliarella had his running speed clocked at 35.07 km/h in August 2021 at the age of 38, which made him one of the fastest players in the Serie A.

[78] In February 2017, Quagliarella revealed in an interview with Mediaset that during his time at Napoli he and his family were threatened by a stalker over a period of five years, which eventually led to his departure from the club.