Guardiola, who won two Champions League titles during four trophy-filled years at Barcelona, took over at Bayern in 2013.
"Of course it's special. I can't say more," Guardiola said. "Barcelona are the best. I am very pleased that I can have this experience."
In the other semifinal, defending champion Real Madrid will face Juventus, with the Italian champions playing at home first. Two-time champion Juventus is back after a 12-year absence from the semifinals, when it also faced Madrid and won.
"They are having a very good season and have practically won the Italian league. That means they can focus more on the Champions League," Madrid coach Carlo Ancelotti said.
The four semifinal teams have combined to win the European Cup or Champions League 21 times, with 16 runner-up finishes, in the competition's 60-year history.
Still, a blockbuster cast of Cristiano Ronaldo, Lionel Messi and the best of Germany's World Cup winning-team will take second billing to Guardiola's return to Camp Nou, where he also won club football's most coveted trophy as a player in 1992.
"Pep is 100 per cent Bayern Munich and that is it," former Bayern great Paul Breitner said. "You (the media) will be focused on Pep. Pep will work as (for) each match in the same way."
The first leg in Barcelona will be played on May 6, with the return match six days later. Madrid will play in Turin on May 5 and host Juventus on May 13.
The final will be played on June 6 at the Olympic Stadium in Berlin.
Guardiola will face his former team in a competitive match for the first time since leaving Barcelona in 2012. His Bayern team won 2-0 in a charity friendly between the sides in Munich soon after he took over.
The two teams also met in the 2013 semifinals while Guardiola was on his one-year sabbatical.
Back then, Bayern humiliated Barcelona, winning 7-0 on aggregate before claiming its fifth European title.
Barcelona is now coached by Luis Enrique, a teammate of Guardiola for five years at the Catalan club.
"It will be the first time I am against Guardiola, and his first time against Barca," Luis Enrique said.
Ten-time champion Real Madrid is aiming to become the first team to win back-to-back titles since the Champions League format began in 1992. And Ancelotti, a former Juventus and AC Milan coach, is looking to become the first man to lead teams to Europe's top club title for a fourth time.
Though Juventus is the lowest-scoring team of the four, it has a typically tight Italian defence, conceding only five goals in 10 matches.
"This Juve is competitive," said club director Pavel Nedved, a standout in the 2003 team. "We know that Real has incredible players but this is a semifinal to play without fear."
In the Europa League, defending champion Sevilla was drawn to play Fiorentina, and Napoli will face Dnipro Dnipropetrovsk.
For the first time, the Europa League winner will also earn a place in the group stage of the Champions League next season.