Early years Mazzarri started his coaching career as
Renzo Ulivieri's assistant at
Napoli in 1998. His first spell in charge came in 2001–02 for
Sicilian Serie C2 team
Acireale, where he had been a player from 1992 to 1994. Subsequently, he returned to his native
Tuscany to coach
Pistoiese of Serie C1 in 2002–03 and
Livorno of
Serie B in 2003–04, bringing the
amaranto led by
Cristiano Lucarelli back to
Serie A. He was coach of
Reggina from 2004 to 2007, leading the
Calabrian side to Serie A survival in three consecutive seasons, the last obtained on the final day of the season despite an 11-point deduction. In May 2007, Mazzarri was made an honorary citizen of
Reggio Calabria, after helping the club avoid relegation during the
2006–07 Serie A season.
Sampdoria On 31 May 2007, he was announced as the new
Sampdoria coach. He served as Sampdoria boss for two seasons, overseeing a considerable improvement in results, thanks to the likes of the attacking duo of
Antonio Cassano, who publicly praised Mazzarri's coaching abilities, and
Giampaolo Pazzini; the duo were likened to the partnership of
Roberto Mancini and
Gianluca Vialli, who won the
scudetto with the club in
1991. Sampdoria's
2007–08 campaign ended in an impressive sixth place, which ensured qualification for the
UEFA Cup. Mazzarri's fortunes declined slightly in
2008–09, as the
Blucerchiati ended their campaign in 13th place; despite this, he managed to guide his team into the
Coppa Italia final, notably defeating champions
Inter 3–1 on aggregate in the semi-finals, before losing on penalties to
Lazio in the final. Mazzarri left Sampdoria by mutual consent at the end of the 2008–09 season. He finished his debut season in sixth place in Serie A, and was handed a new three-year contract at the end of the campaign. In
2010–11, Mazzarri's Napoli finished third in the league and qualified directly for the group phase of the
2011–12 UEFA Champions League – their first time in Europe's premier competition in 21 years. His team were known for using an attacking 3–4–3 formation with a frontline three of
Ezequiel Lavezzi,
Marek Hamšík and
Edinson Cavani, who were nicknamed
I tre tenori ("
The Three Tenors"); Mazzarri also employed variations upon this system on occasion, such as
3–5–2 formation, the
3–4–1–2, and the
3–5–1–1. They finished second in their Champions League group, behind
Bayern Munich but ahead of
Manchester City and
Villarreal, to meet
Chelsea in the last 16. Napoli won 3–1 at home in the first leg; they were subsequently beaten 4–1 at
Stamford Bridge after extra time, being eliminated by the eventual champions. Napoli won the
2012 Coppa Italia final over undefeated
league champions Juventus on 20 May; this was Juventus's only loss of the season, and Napoli's first title in over 20 years. On 11 August that year, the club suffered a controversial 4–2 extra-time defeat to Juventus in the
2012 Supercoppa Italiana, which saw two Napoli players sent off as well as Mazzarri. He left the
Azzurri on 19 May 2013, after leading them to a 2nd-place finish and a spot in the Champions League at the end of the
2012–13 Serie A season; this was the club's best league finish in over 20 years.
Inter Milan Mazzarri was officially appointed as the
Inter manager on 24 May 2013, after
Andrea Stramaccioni was dismissed for a poor performance in the 2012–13 season. On 2 July 2014, he signed a one-year extension to tie him to the team until 30 June 2016. He was sacked by Inter after a series of disappointing results on 14 November 2014, leaving the club in ninth place. He parted with the club before the 12th matchday, while they were five points below their season objective of the third position.
Watford On 21 May 2016,
Watford confirmed they had reached an agreement with Mazzarri to become head coach from 1 July 2016 on a three-year contract. He joined a club owned by his compatriot
Giampaolo Pozzo, and worked without being able to speak English. Mazzarri secured Watford's Premier League status that season, finishing one place above relegation in 17th, a four-place dip on their previous campaign.
Torino On 4 January 2018, Mazzarri was appointed manager of
Torino, replacing
Siniša Mihajlović. With a 7th-place finish in 2018–19 he led the
Granata to the
UEFA Europa League, where they were eliminated in the play-off round by
Wolverhampton Wanderers. On 4 February 2020, Mazzarri was dismissed following back-to-back 7–0 and 4–0 defeats to
Atalanta and
Lecce, respectively.
Cagliari On 15 September 2021, Mazzarri signed a three-year contract with
Serie A club
Cagliari as their new head coach, replacing
Leonardo Semplici. During his tenure, Cagliari failed to improve performances and found themselves deep in relegation trouble with three games to go, leading to Mazzarri's dismissal from his position on 2 May 2022.
Second stint at Napoli On 14 November 2023,
Napoli appointed Mazzarri as their new head coach on a seven-month contract, replacing
Rudi Garcia, marking Mazzarri's return to Naples after ten years. He was sacked on 19 February 2024, after a 1–1 home draw to
Genoa. ==Style of management and reception==