Aitor Karanka praised the club's work behind the scenes with a host of players arriving before the team jetted out to Marbella for their annual training camp, and still more joining before the start of the league season.
New faces continued to arrive at Rockliffe right up until Wednesday's transfer deadline, with Boro one of the most active teams across the country.
Here's our overview of all the transfer movement at the club this summer.
Aitor Karanka's first summer acquisition was Danish international Viktor Fischer. The exciting winger joined from Dutch giants Ajax on a three-year deal.
Boro then swooped to sign Colombian Bernardo Espinosa on free transfer. The central defender had been playing with Sporting Gijon in La Liga.
Marten de Roon was next to join Boro's ranks. After winning the club's Player of the Year award in his single season with Serie A side Atalanta, combative Dutch midfielder De Roon joined on a four-year deal.
Scotland U21 captain Jordan McGhee also joined the club's youth setup on a season-long loan from Heart of Midlothian.
Barcelona legend Victor Valdes was next to join, on a two-year contract. The Spanish keeper, a Champions League and World Cup winner, left Manchester United earlier in the summer.
Boro then sealed the signatures of Spanish duo Antonio Barragan and Alvaro Negredo from Valencia. Right-back Barragan joined on a permanent basis, signing a three-year deal, while former Manchester City forward Negredo arrived on a season-long loan.
The Teessiders' Premier League squad was bolstered further with the return of Uruguayan Gaston Ramirez on a three-year contract. Ramirez had helped the club seal promotion from the Championship during a spell on loan from Southampton last season.
Former Aston Villa goalkeeper Brad Guzan was the next arrival at Rockliffe. Boro agreed a two-year deal with the experienced US international.
Aitor Karanka boosted his defensive options with the capture of Brazilian Fabio da Silva. The full-back signed from Cardiff City for an undisclosed fee, penning a two-year contract.
Calum Chambers completed Boro's defensive acquisitions, with the versatile England international joining on a season-long loan from Arsenal.
Boro's final arrival of the summer window was jet-heeled winger Adama Traore. Adama was recruited from Aston Villa for an undisclosed fee on deadline day, putting pen to paper on a four-year deal, with Albert Adomah heading in the opposite direction.
In addition to the incomings, the club also made moves to strengthen from within and George Friend, Ben Gibson, Daniel Ayala, Adam Forshaw and Dael Fry all pledged their futures to the club by signing new long-term contracts.
Following Boro's promotion campaign, veteran defender and club legend Jonathan Woodgate announced his retirement from football, while Damia Abella also departed the club.
After more than a decade on Teesside, Rhys Williams also left Boro, returning to his native Australia with Perth Glory.
Academy players Andre Bennett, Jordan Jones and Luke Coddington ended their time with Boro. The trio were released by the club, and subsequently joined Bishop Auckland, Kilmarnock and Huddersfield Town respectively.
Adam Jackson and Bradley Halliday also left Boro in permanent transfers having come through the ranks of the club's Academy. Jackson signed for newly-promoted Barnsley in the Championship, while Halliday joined League Two Cambridge United.
Four Academy youngsters headed out to gain loan experience. Jonathan Burn linked up with Jordan Jones at Kilmarnock, Harry Chapman headed to Sheffield United in League One, Connor Ripley also made the switch to the third tier with Oldham Athletic, and Bradley Fewster signed for North East neighbours Hartlepool United. Burn and Fewster will return to Boro in January, while Chapman and Ripley will remain at their new clubs for the season.
A trio of Boro players made moves to the Championship on deadline day.
The club reached a mutual agreement with Muzzy Carayol to terminate the winger's contract. The Gambia international then joined Nottingham Forest.
Albert Adomah also left Boro on deadline day, sealing a permanent move to Aston Villa.
Alex Baptiste headed out on a season-long loan, linking up with former manager Simon Grayson at Preston North End.
Two final moves on deadline day saw Adam Reach join Sheffield Wednesday in a permanent deal while Dael Fry signed a new five-year contract with Boro before joining Rotherham United on a season-long loan.