In
1979–80, the club first competed in the
top division, finishing in 13th position and being relegated. On 16 April 2001, the club appointed former
Benfica manager
José Mourinho on a two-year contract. In January 2002, having taken the team as high as third, he departed for
Porto. His successor
Mário Reis resigned after five games, having lost four, and the team concluded the season in seventh under
Vítor Pontes. The club lost the
2003 Taça de Portugal final to Mourinho's Porto, with the only goal coming from ex-União de Leiria striker
Derlei. As the northern club had won the
double of league and cup, União de Leiria were their opponents in the
2003 Supertaça Cândido de Oliveira on 10 August, with the same scoreline. União de Leiria reached the
2004 UEFA Intertoto Cup final with
Lille. After goalless draws in France and at home, the team lost 0–2 in extra time on 24 August.
Three years later, the club won the same event with a 4–1 second-leg win over Serbia's
Hajduk Kula reversing a 1–0 away loss. After defeating Israel's
Maccabi Netanya by a single goal in the qualifying round, the club took on
Bayer Leverkusen in the first round of the
UEFA Cup, losing 5–4 on aggregate with a 3–2 home win in the second leg. In
2007–08, the club was relegated to the
second level, after finishing last; it was additionally involved in the
Apito Dourado scandal. The
2011–12 season was lived amongst serious financial difficulties, with the squad not being paid their wages for several months, as three coaching moves also happened during the campaign and president João Bartolomeu resigned amongst accusations of ingratitude towards the players. On 29 April 2012, after most of the squad rescinded their contracts, only eight players took the pitch for the league match at home against
Feirense in an eventual 0–4 home loss. The side played the last two matches, against
Benfica and
Nacional, with a complete team, but three players came from the juniors. After failing to meet the deadline to register the team in Division Two, Leiria were automatically relegated to the
third level. Overwhelmed with the task of rebuilding a squad from scratch, the organization hired several players in an attempt to return to the professionals, as a second senior team also begun competing in the
Leiria regional leagues, coached by former club player
Luís Bilro. On 28 June 2013, the UD Leiria
SAD was declared
bankrupt in a meeting of
creditors, which demanded the payment of a debt amounting to €13.5 million, with the Portuguese state
abstaining for demanding a debt of over €3.6 million. The second senior team that competed in the regional league took the place of the SAD by buying their sports rights for €1,000, with the club returning to the
Estádio Dr. Magalhães Pessoa after playing their home matches at other grounds for two seasons. In February 2015, at an extraordinary general assembly, UD Leiria would vote for the creation of another SAD, opening doors to the arrival of Alexander Tolstikov, who after João Bartolomeu would become the new "Lord" of Leiria. The club would have already had a SAD between 1999 and 2013, having been extinguished in the face of its high debt value. The SAD's initial share capital is 40% owned by UD Leiria and 60% owned by DS Investment LLP, of which Alexander Tolstikov is one of those responsible. Thus, DS Investment started to control the main football team and also the junior team. In October 2020, after a vote at a general meeting, the members approved the entry of a new investor into the club's SAD: Armando Marques, a former director of
Vitória de Guimarães. Furthermore, they waived their right of first refusal in the sale of 60% of DS Investment LLP, a company owned by Alexander Tolstikov, leading to their departure from the SAD structure. In
2022–23, the club won
Liga 3 and promotion to
Liga Portugal 2. The team defeated
Belenenses 1–0 at the
Estádio Nacional to return to professional leagues for the first time since 2012. ==Players==