Joao Moutinho's second-half goal ensured Monaco's return to the Champions League after a 10-year absence ended in victory against Bayer Leverkusen at the Stade Louis II.
Monaco, back in the Champions League group stages for the first time since the 2004/05 season, were second best for much of the contest but Moutinho's 61st-minute goal settled the match after Leverkusen had wasted a number of chances to take the lead.
The 1-0 victory gives Leonardo Jardim's side an encouraging start to Group C action ahead of a difficult trip to Saint Petersburg to face Andre Villas-Boas' Zenit side in a fortnight's time.
Monaco nearly made the perfect start when, in the second minute, Yannick Carrasco went down under a clumsy Gonzalo Castro challenge in the penalty area but referee Pavel Kralovec waved away the hosts' claims for a penalty.
Leverkusen gave a glimpse of their attacking threat in the 13th minute, but Castro was uncharacteristically wayward when teed up by Son Heung-min after a trademark mazy run down the left flank by the South Korea forward.
The Germans were wasteful once again in the 35th minute when an intricate reverse pass by Hakan Calhanoglu found fellow midfielder Karim Bellarabi in space behind the Monaco backline, but his chip over Monaco goalkeeper Danijel Subasic drifted wide.
Calhanoglu had two clear-cut chances in the closing stages of the first half but could not give Leverkusen a well-deserved lead.
First, Monaco centre-back Ricardo Carvalho threw his body on the line to block a long-range effort from the Turkey international that appeared destined for the back of the net.
Then, after Layvin Kurzawa was booked for hauling him down, Calhanoglu dragged his second shot wide of the target and, much to Monaco's relief, it remained goalless as the half-time whistle sounded.
The second half began in lacklustre fashion with Castro's speculative effort from distance the only chance of note in first 10 minutes after the restart.
Leverkusen still had the upper hand which prompted Monaco boss Jardim to replace Lucas Ocampos with Bernardo Silva in the 57th minute and the hosts took the lead four minutes later.
Layvin Kurzawa darted down the left wing before whipping in a pin-point cross which Dimitar Berbatov flicked into the path of Moutinho, who coolly slotted home from inside the penalty area.
Roger Schmidt introduced Giulio Donati, Stefan Reinartz and Josip Drmic as Leverkusen chased an equaliser but despite having the majority of possession after conceding, they could not carve out any further clear-cut chances and Monaco hung on for victory.