The team went on to win the provincial championship in five of its first ten seasons of competition (1959-69) and achieved the promotion to the 3rd division after Pepe Laso took over as head coach, prevailing over city rival Deportivo Alavés.

The team finished in eighth place and gained the right to play in the Korać Cup but declined to participate on financial grounds.

The team incorporated young players such as Manu Moreno, Kepa Segurola, Luis María Junguitu, Carlos Salinas, and José Antonio Querejeta, and signed American Ray Price, who became the division's top scorer.

The team adopted the Basque national colors of the Ikurriña, green with red and white trim instead of the club's traditional blue and maroon.

[3] In 1977, Juan Antonio Ortiz de Pinedo retired as a player to become the head coach of the team, replacing Pepe Laso.

Players like Junguitu, and Txomin Sautu returned and Juan Manuel Conde was signed, along with the American Webb Williams.

Fernando Aranguiz assumed the presidency of the club in June 1978 and Carlos Luquero was honored for a professional record including more than 300 games and more than 7,000 points with the team.

[3] In 1979, Peio Cambronero arrived from Estudiantes and the club signed the American Malcolm Cesare, but the results for the 1979–80 season were not good and the team finished the league in a relegation position.

Fortunately, the Spanish Federation decided to expand the 1st division to fourteen teams, allowing Club Deportivo Basconia to remain in the league.

[4] In the summer of 1981, José Antonio Querejeta, who had returned to the team after passing through Real Madrid and had been tested by FC Barcelona, was transferred to Joventut.

Spanish basketball was preparing to enter a new stage marked by professionalism, and the creation of the Liga ACB made it possible for the team to avoid relegation back to the 2nd Division.

[4] In 1985, the club won its first official title, the Copa Asociación which was played among the teams eliminated in the first round of the league playoffs.

José Antonio Querejeta was the top scorer of the game with 30 points and the team earned the qualification to the Korać Cup for the following season.

Larry Micheaux and David Lawrence formed the American couple, but the weak performance of the second led to its replacement by the jumpy Nikita Wilson midway through the season.

Herb Brown signed as head coach and Alfredo Salazar began his travels through Argentina to capture talent.

In 1991, the club left Polideportivo Mendizorrotza to move to the Araba Arena, which lived its extension from 5,000 to 9,500 spectators at the end of the decade.

Names like Ramón Rivas, Marcelo Nicola, Juan Alberto Espil, Pablo Laso, Elmer Bennett or Velimir Perasović were some of the protagonists of that decade.

Baskonia snatched two more Spanish King's Cups, in 2004 and 2006, as Luis Scola and Pablo Prigioni played decisive roles, and success followed the team in the EuroLeague.

In the 2009–10 season, Baskonia won its third Spanish Liga ACB championship by sweeping FC Barcelona on a memorable series-winning three-point play by Fernando San Emeterio.

Igor Rakočević, Arvydas Macijauskas, José Calderón, Pete Mickeal or Tiago Splitter were some of the protagonists of that decade.

Ádám Hanga was one of the team leaders and was chosen as the EuroLeague Best Defender by the league's head coaches, and Baskonia showed, once again, its innate ability to sign talent that seemed to go under the radar for everybody else with names like Shane Larkin, Johannes Voigtmann and Rodrigue Beaubois playing major roles.

[8] In the 2017–18 season, the club advanced to the playoffs for the third consecutive year and put up a major fight against Fenerbahçe before falling in four games.

The man appointed to turn things around was Pedro Martínez, who immediately effected a remarkable revival as Baskonia won four of its next five games to ignite its challenge.

A mid-season dip left the side in the bottom half of the standings heading into the final few weeks of the regular season, but then came a dramatic surge in form that yielded six consecutive win, with the consistent excellence of versatile big man Tornike Shengelia earning him the monthly MVP award for March.

A top half finish was sealed with a home win over Maccabi Tel Aviv in Round 29, and although disappointment followed against Fenerbahçe, that playoff berth was a just reward for Baskonia's typically spirited recovery from its slow start.

The team was also highly competitive on the domestic front, earning a second-place finish in the Spanish League after pushing Real Madrid hard in the finals.

A slow start caused Baskonia to part ways with head coach Pedro Martínez and bring back club legend Velimir Perasović to replace him.

Baskonia kept struggling on the road, but won 10 of its last 11 regular season games – including victories against playoff-bound teams CSKA Moscow, Panathinaikos and Real Madrid – to reach the playoffs from sixth place.