The 2013 quarter-finalists scored three second-half goals on their way to a comfortable 4-1 victory over Al Kuwait.
Sebastian Soria opened the scoring shortly prior to the half-hour mark, before Javad Nekounam levelled from the spot five minutes later.
Youssef Msakni found himself in plenty of space to slot the ball into the bottom right-hand corner midway through the second half to re-establish Lekhwiya's lead, before Karim Boudiaf and Luiz Junior put the game beyond doubt - Msakni providing the assist for both.
The win sends them into Group C, alongside Al Ain, Al Ittihad and Tractorsazi.
Fellow Qatari outfit El Jaish joined them in the main draw after a 3-0 victory over Al Qadsia.
Nilmar broke the deadlock nine minutes before the break, while Mohammed Munatri and Mohammed Jeedo found the net in the second half.
El Jaish now join Al Fateh, Foolad and Bunyodkor in Group B.
Beijing Guoan of China will enter Group F with Sanfrecce Hiroshima, Central Coast Mariners and Seoul after they cruised past 10-man Chonburi of Thailand in a 4-0 victory.
Three goals in 18 first-half minutes left Chonburi reeling, and Shao Jiayi completed the job with an 89th-minute strike, before Thiago Cunha was given his marching orders at the end.
The remaining Champions League berth went to Australia's Melbourne Victory, who edged a tight encounter against Muangthong United 2-1.
The Thai side broke the deadlock via a close-range header from Macedonian Mario Durovski in the 22nd minute, before Melbourne's Mark Milligan saw a penalty kick saved.
However, the A-League outfit bounced back - James Troisi heading home just before the hour mark and midfielder Leigh Broxham firing in a 20-yard strike seven minutes from time.
Muangthong captain Datsakorn Thonglao was sent off in stoppage time for headbutting goalscorer Broxham.
Melbourne will take on Guangzhou Evergrande, Yokohama F Marinos and Jeonbuk in Group G of the competition.
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