[2] On 29 June 2017, club president Luís Filipe Vieira gave the motto for the coming season, "Rumo ao Penta", and promised a renewed ambition to conquer an unprecedented fifth-straight Primeira Liga title for Benfica.

[3] The following day, manager Rui Vitória explained his approach to the new season: "We know that there's a goal previously assumed by the President and the best way to achieve it is to go on together, like it was the first time.

Diogo Gonçalves and Rúben Dias were promoted from Benfica B and João Carvalho integrated the team after a loan spell at Vitória de Setúbal.

On transfer deadline day, Benfica announced the signings of Douglas and Gabriel Barbosa, both on a one-year loan spell from their respective clubs.

The same day, Kostas Mitroglou, Benfica's top goalscorer in the previous season, was transferred to Olympique de Marseille for €15 million.

During the mid-season transfer window, Lisandro López signed with Inter Milan on a half-year loan deal with an option to make the switch permanent.

The pre-season started on 30 June 2017 with the usual medical exams and physical tests at Caixa Futebol Campus and at Hospital da Luz.

As for the team's commitments, the program included the Uhrencup in Switzerland, a five-day stay in Algarve with two matches, and a stage at St George's Park in England, from 23 to 28 July, before the Emirates Cup.

On 17 June, Álex Grimaldo did not take part in Spain's squad for the UEFA European Under-21 Championship due to a "little injury" resulting in him missing the start of Benfica's pre-season.

[11] He was one of three players absent from the squad who travelled to Switzerland, along with Luisão (right knee injury) and Eduardo Salvio (right tibiotarsal sprain).

[13] For the opening match of the regular season, Benfica had five players on the injury list: Júlio César, Živković, Carrillo, Horta and Mitroglou.

[19] A 1–1 draw at Rio Ave, in a match where Jardel was substituted due to injury on his right tight,[20][21] left Benfica in third place of the league by the end of August.

After losing 2–1 at Boavista and drawing 1–1 with Marítimo at the Estádio dos Barreiros, Benfica were 5 points behind leaders Porto before October's international break.

It was the fourth match in a row Benfica could not beat Porto at the Estádio da Luz (two draws and two defeats), a negative record achieved for the third time.

[28] With a 3–2 home loss to Tondela, Benfica suffered two consecutive league defeats at Estádio da Luz for the first time since the 2008–09 season.

[29] With a 1–0 home win against Moreirense on the last matchday, Benfica attained 80+ points in the Primeira Liga for the fourth consecutive season.

Due to the defeat of Sporting CP at Funchal, Benfica's result allowed the club to secure the second place and the qualification for the 2018–19 UEFA Champions League third qualifying round.

It was Benfica's biggest defeat in the UEFA Champions League (tied with the loss to Borussia Dortmund in the 1963–64 European Cup) and second overall in international competition.

On 18 October, Svilar became the youngest goalkeeper to play in Champions League,[32] in a match where Benfica suffered a 1–0 home loss against Manchester United.

By failing to score, Benfica put an end to Igor Akinfeev's streak of 43 straight UEFA Champions League group stage matches without a clean sheet.

[36] Four players (Júlio César, Eliseu, Jardel and Jonas) missed the game due to injury,[37] while Douglas, Carvalho and Svilar made their debut for Benfica.

After a 2–2 draw at the end of regulation time, Hélder Guedes scored the winning goal for Rio Ave, thus eliminating the reigning title holders.

[39] On 11 June, Vieira regretted the club's disappointing season overall and took responsibility for not managing to win the penta and for the negative campaign in the Champions League.

Five Benfica players were called by their respective national team to take part in the 2018 FIFA World Cup: Dias (Portugal), Salvio (Argentina), Živković (Serbia), Seferovic (Switzerland) and Jiménez (Mexico).

[65][66] It was scheduled to take place in Canada on 6 October, but Benfica announced its cancellation on 30 September due to the promoters' (Elite Soccer Entertainment) non-compliance with deadlines.

[72] Initially, Real was drawn into group A of the Taça da Liga; however, due to the irregular use of Abou Touré, the Disciplinary Committee of the Portuguese Football Federation awarded the team with an administrative loss in their second round match.