Early career Born in
Valdobbiadene,
Province of Treviso,
Veneto, Longo started his career at
Treviso FBC 1993. He was the member of
Esordienti under-13 team in 2004–05 season. In January 2009
Inter Milan bought Longo and
Mame Baba Thiam outright. Longo spent the rest of 2008–09 season in Treviso's
Allievi Nazionali under-17 team in a temporary deal before formally became an Inter player on 1 July 2009.
Inter Milan Youth ;2009–10 Longo was a junior member of Inter's
reserve team in the 2009–10 season, as a backup for
Denis Alibec,
Mattia Destro and
Simone Dell'Agnello. On 28 January 2010, after being sparingly used by Inter, he left for
Piacenza Calcio, along with Giuseppe Angarano and
Luca Stocchi. In total, Longo only played 4 times in the
reserve league that season. ;2010–11 In the 2010–2011 season, despite Inter trimming their reserve squad (only composed only of U18 and U19 players plus 3 U20), Longo was unable to become a regular starter, with 11 appearances, (2 starts) and 2 goals. In January 2011 he moved to
Genoa in a temporary deal with option to sign Longo in
co-ownership deal, also as a replacement of outgoing reserve forward
Gianmarco Zigoni. Longo scored 3 goals for Genoa and 2 goals for Inter in 2010–11 reserve league. He also appeared in the league's play-offs, losing to eventual champions Roma in the semifinals, forming a partnership with
Richmond Boakye; his side was also eliminated by Inter in the quarter-finals of
2011 Torneo di Viareggio. ;2011–12 In June 2011 Genoa signed Destro outright from Inter for €4.5M, as well as half of the registration rights of Longo for a peppercorn fee of €500 (also made Inter had to write-down €47,000 for the residual accounting value of his contract). He returned to Inter in temporary deal on 1 July 2011, being again assigned to the reserves. Longo was a regular starter for the side, but was unable to be the topscorer, scoring eight goals times during the regular season (attacking midfielder
Daniel Bessa eventually scored ten times). Under
Andrea Stramaccioni, Longo scored 5 goals in
2011–12 NextGen series as one of the team that won the tournament; his role also sightly changed after the arrival of
Marko Livaja as new centre forward, in 4–2–3–1 (and later 4–3–3/4–3–2–1 formation under
Daniele Bernazzani). He was also instrumental in the
Primavera final stages, netting four goals in three matches (including a brace in the final against Lazio).
First-team ;2011–12 Longo was assigned number 81 shirt at the start of 2011–12 season, and played the first four friendlies of the season under former Genoa first team coach
Gian Piero Gasperini. However he was left out of the squad submitted for
2011–12 UEFA Champions League, with
Giovanni Terrani being included instead. Longo made his professional debut on 13 May 2012, playing the last 14 minutes of a 1–3 away loss against
Lazio. ;2012–13 Longo scored his first goal for Inter against
Indonesia League Selection on 24 May 2012. In June 2012, Genoa CEO Pietro Lo Monaco once confirmed the co-ownership was renewed but on the deadline date Internazionale bought back Longo for €7 million and sold
Juraj Kucka back to Genoa for €6.5 million. Longo made his international debut on 9 August, coming on as a second half
substitute in a 0–2 home loss against
Hajduk Split for
the season's
Europa League.
Loan to Espanyol On 28 August 2012, Longo joined Spanish side
RCD Espanyol of
La Liga on a season-long loan deal, following in the footsteps of Internazionale teammate
Philippe Coutinho, who spent the final six months of the 2011–12 campaign at
Estadi Cornellà-El Prat. On 2 September he made his debut abroad, scoring the first of a 2–3 away loss against
Levante. Longo scored his second goal on the 16th, in a 3–3 home draw against
Athletic Bilbao, but was later
sent off due to his celebration. Longo's third goal for the
Catalans came on 17 November, but in a 1–2 away defeat against
Valencia CF. He finished
the season with 18 appearances, including 11 starts.
Loan to Verona On 20 August 2013 Longo joined
Verona,
recently promoted to Serie A, in a season-long loan deal. However, he only appeared twice in
the season (against
Cagliari and
Roma), all from the bench.
Loan to Rayo Vallecano On 31 January 2014 Longo joined fellow top-divisioner
Rayo Vallecano on loan until the end of the season.
Loan to Girona On 16 July 2016, after another loan stints at
Cagliari and
Frosinone, Longo was loaned to Spanish
Segunda División side
Girona FC for one year. He made his debut on 21 August, a debut which brought his first goal of the season as well, in a 3–3 away draw against
Sevilla Atlético, in the opening league match of
2016–17 season. At the end of 2016–17 season, Longo returned to Inter. He was part of the squad in the first day of pre-season training.
Loan to Tenerife On 23 August 2017, Longo was sent on loan at fellow Segunda División side
Tenerife for the
2017–18 season.
Loan to Huesca On 5 July 2018, Longo was loaned to
SD Huesca,
newly promoted to La Liga, on a one-year deal with an obligation to make it permanent.
Loan to Cremonese On 30 January 2019, Longo joined
Serie B side
Cremonese on loan until 30 June 2019 with an obligation to make the deal permanent if Cremonese won promotion to
Serie A.
Loan to Deportivo La Coruña On 16 August 2019, Longo joined Spanish side
Deportivo La Coruña on loan until 30 June 2020 with an obligation to make the deal permanent if the club won promotion to
La Liga.
Loan to Venezia On 31 January 2020, Longo joined
Serie B club
Venezia on loan until 30 June 2020.
Vicenza On 5 October 2020, he signed a three-year contract with
Serie B club
Vicenza.
Loan to Modena On 31 January 2022, Longo joined
Modena on loan with an option to buy and a conditional obligation to buy.
Dordrecht On 3 August 2022, Longo moved to
Dordrecht in the Netherlands.
Antequera On 29 January 2025, Longo returned to Spain and signed with
Antequera in the
third tier until the end of the season, with an option to extend.
Xerez Deportivo On 28 January 2026, Longo signed with Spanish
fourth-tier club
Xerez Deportivo. ==International career==