| | Event type
Lightweight (≤71 kilograms), Men
| Date | 6 August 1984 — 16:00-20:00 | |
|---|---|---|
| Status | Olympic | |
| Location | Eagle's Nest Arena, California State University at Los Angeles, Los Angeles, California | |
| Participants | 31 from 31 countries | |
| Format | Two single-elimination pools, with winner of each pool advanced to the final. All judoka losing to the winner of each pool advanced to repêchage pools, with the winners of the repêchage pools earning bronze medals. | |
The defending champion was Italy’s Ezio Gamba, who had placed second at the 1983 World Championships to Japan’s Hidetoshi Nakanishi. They were the two favorites and this class was one on which the boycott had minimal effect. In the first round, Nakanishi had difficulty with the Senegalese Ibrahima Diallo. Nakanishi won but broke a rib in the process and would not win a medal. Gamba started out with a tough match against Serge Dyot (FRA), the 1984 European runner-up. But Gamba had little trouble, Dyot eventually submitting – twice, as the referee did not notice the first submission. Gamba made the final where he faced Korean An Byeong-Geun. Gamba was favored but An scored two kokas early on, and was able to hold off Gamba to win the gold medal.
Pool A (6 August 1984)
Round One (6 August 1984)
| Match #1 | Glenn Beauchamp |  CAN | bye | ||
| Match #2 | Yi Dexin |  CHN | Waza-ari awasete Ippon/Kami-shiho-gatame (3:41) | Tam Chin Kee |  HKG |
| Match #3 | Johannes Wohlwend |  LIE | Waza-ari/Te-guruma (5:00) | Shaun O'Leary |  NZL |
| Match #4 | Ezio Gamba |  ITA | Ippon/Kansetsu-juji-gatame (1:07) | Serge Dyot |  FRA |
| Match #5 | Hassan Ben Gamra |  TUN | Ippon/Uchi-mata (0:42) | Rony Khawam |  LBN |
| Match #6 | Luiz Onmura |  BRA | Ippon/Uchi-mata (3:18) | Yousry Zagloul |  EGY |
| Match #7 | Mike Swain |  USA | Yusei-gachi [3/3] (5:00) | Frank Evensen |  NOR |
| Match #8 | Yousuf Al-Hammad |  KUW | Ippon/Kansetsu (2:58) | Jean Claude N'Guessan |  CIV |
Quarter-Finals (6 August 1984)
| Match #1 | Glenn Beauchamp | CAN | Yuko/Te-waza (5:00) | Yi Dexin | CHN |
| Match #2 | Ezio Gamba | ITA | Ippon/Kansetsu-juji-gatame (2:02) | Johannes Wohlwend | LIE |
| Match #3 | Luiz Onmura | BRA | Waza-ari/Seoi-nage (5:00) | Hassan Ben Gamra | TUN |
| Match #4 | Mike Swain | USA | Ippon/Uchi-mata (0:04) | Yousuf Al-Hammad | KUW |
Semi-Finals (6 August 1984)
| Match #1 | Ezio Gamba | ITA | Ippon/Kansetsu-juji-gatame (0:42) | Glenn Beauchamp | CAN |
| Match #2 | Luiz Onmura | BRA | Yusei-gachi [3/3] (5:00) | Mike Swain | USA |
Final Round (6 August 1984)
| Match #1 | Ezio Gamba | ITA | Ippon [unknown] | Luiz Onmura | BRA |
Repêchage (6 August 1984)
| Match #1 | Serge Dyot | FRA | Yuko/Tai-otoshi (0:58) | Johannes Wohlwend | LIE |
| Match #2 | Glenn Beauchamp | CAN | Yusei-gachi [3/3] (5:00) | Serge Dyot | FRA |
| Match 3/4 | Luiz Onmura | BRA | Koka/Kaeshi-waza (7:00) | Glenn Beauchamp | CAN |
Pool B (6 August 1984)
Round One (6 August 1984)
| Match #1 | Liaw Der-Cheng |  TPE | Yuko-chui/Penalty (5:00) | Michael Young |  AUS |
| Match #2 | Joaquín Ruiz |  ESP | Waza-ari awasete Ippon/De-ashi-barai/Seoi-nage (2:19) | Álvaro Sanabria |  CRC |
| Match #3 | Steffen Stranz |  FRG | Ippon/Uchi-mata (1:07) | Antti Hyvärinen |  FIN |
| Match #4 | Kerrith Brown |  GBR | Yusei-gachi [2/3] (5:00) | Vojo Vujević |  YUG |
| Match #5 | Hidetoshi Nakanishi |  JPN | Hansoku-gachi (4:24) | Ibrahima Diallo |  SEN |
| Match #6 | Federico Vizcarra |  MEX | Waza-ari/Ko-uchi-gari (5:00) | Hugo d'Assunção |  POR |
| Match #7 | Juan Vargas |  ESA | Ippon/O-goshi (4:56) | Alick Kalwihzi |  ZAM |
| Match #8 | An Byeong-Geun |  KOR | Ippon/Yoko-shiho-gatame (2:53) | Kieran Foley |  IRL |
Quarter-Finals (6 August 1984)
| Match #1 | Liaw Der-Cheng | TPE | Yuko-chui/Penalty (5:00) | Joaquín Ruiz | ESP |
| Match #2 | Kerrith Brown | GBR | Ippon/Ude-garami (4:25) | Steffen Stranz | FRG |
| Match #3 | Hidetoshi Nakanishi | JPN | Waza-ari/De-ashi-barai (5:00) | Federico Vizcarra | MEX |
| Match #4 | An Byeong-Geun | KOR | Waza-ari awasete Ippon/Seoi-nage (0:36) | Juan Vargas | ESA |
Semi-Finals (6 August 1984)
| Match #1 | Kerrith Brown | GBR | Koka/Seukui-nage (5:00) | Liaw Der-Cheng | TPE |
| Match #2 | An Byeong-Geun | KOR | Yuko-chui/Penalty (5:00) | Hidetoshi Nakanishi | JPN |
Final Round (6 August 1984)
| Match #1 | An Byeong-Geun | KOR | Yusei-gachi [3/3] (5:00) | Kerrith Brown | GBR |
Repêchage (6 August 1984)
| Match #1 | Kieran Foley | IRL | Ippon/Uchi-mata (0:08) | Juan Vargas | ESA |
| Match #2 | Hidetoshi Nakanishi | JPN | Yuko/Kaeshi-waza (5:00) | Kieran Foley | IRL |
| Match 3/4 | Kerrith Brown | GBR | Koka/Ko-uchi-gari (7:00) | Hidetoshi Nakanishi | JPN |
Final Round (6 August 1984)
| Match 1/2 | An Byeong-Geun | KOR | Koka/Seoi-nage (7:00) | Ezio Gamba | ITA |