In the fall of 1988, Pereira registered wins on the pro tour against Brad Gilbert and Amos Mansdorf. He finished 1988 ranked no. 151 in the world rankings. In April 1989, Pereira reached the quarterfinals of the Tokyo Japan Open, beating no. 21 ranked Andrés Gómez, then lost to no. 1 ranked Ivan Lendl. In June, he beat world no. 3 Stefan Edberg in straight sets in the first round of the Queens Clubgrass court tournament. A few weeks later, in the first round of Wimbledon, he took Lendl to five sets before losing. Later that summer, he reached the quarterfinals of the Grand Prix event at Montreal, the Canadian Open. There he beat no. 10 ranked Tim Mayotte, then lost to no. 14 ranked Jay Berger. Pereira, at 19 years of age, finished 1989 ranked no. 121. However, Pereira's progress was stalled over the next three years. In 1990, he lost most of his matches in the first round of ATP level tournaments and finished the year ranked no. 238. In 1991, he did win the Lins and São Paulo-4 Challengers in back-to-back weeks, and was ranked no. 146 at year's end. He won the Guarujá Brazil Challenger in September 1992 and was ranked no. 138 at the end of the year. In 1993, Pereira defeated Aaron Krickstein in the first round at the Bermuda Challenger. At the end of 1993, Pereira was ranked no. 141. 1994 marked a resurgence for Pereira. In March, he won the San Luis Potosí Challenger. At Wimbledon, he reached the second round where he lost a thrilling five set match to no. 18 Andre Agassi. In September, Pereira beat Mauricio Hadad at the ATP Bogotá to register his first ATP tournament title. He closed out 1994 ranked no. 110. 1995 was a mixed year for Pereira. In July, he won the Rio Brazil Challenger title by defeating Joao Culna-Silva in straight sets. The next week at New Haven, he defeated MaliVai Washington in the second round, then lost to no. 10 Marc Rosset. At the U.S. Open, Pereira reached the third round of a Grand Slam tournamentfor the first time. At the end of the year, Nicolas was ranked no. 134. 1996 was another inconsistent year for Pereira. He started the year well in Doha by qualifying, then beating world no. 5 Boris Becker 7–6, 6–7, 7–6 in round two. In March, Pereira again caused an upset when he beat world no. 1 Thomas Muster in straight sets at the Masters Series tournament in Key Biscayne, Florida. In July, Pereira won his second career ATP title when he beat Grant Stafford on the grass courts at Newport, Rhode Island. He reached his highest singles ATP-ranking on July 22, 1996 when he became the no. 74 player in the world. He represented Venezuela at the 1996 Summer Olympics in Atlanta. Pereira had mediocre results during the rest of the 1996 season, and finished the year ranked no. 110. Reportedly suffering from injuries, Pereira retired in September 1997, ranked around world no. 400.
