A tie-up has been on and off the cards for years as the companies look to create a stronger business and make savings.
They abandoned talks in November after failing to agree on a share exchange ratio. Immofinanz now says it is open to new talks, though the coronavirus pandemic complicates the timeframe.
In February, an investment vehicle partly owned by Pecik bought 10.7% in Immofinanz from Vice Chairman Rudolf Fries, who left the company in early March. Long-serving Chief Executive Oliver Schumy left shortly afterwards, citing personal reasons.
Pecik, a 58-year-old Austrian born in Croatia, and a partner hold around 14% in S Immo, and the two groups are already interlinked, with Immofinanz holding 29% in S Immo, and the smaller firm holding 12% in Immofinanz.
"Ronny Pecik is a leading entrepreneur and his many years of experience in executive and supervisory board positions carry a special strengthening of the executive board in challenging times like these," Immofinanz's supervisory board Chairman Michael Knap said in a statement.
"Further there is also a strong entrepreneurial responsibility grounded in the significant stake in Immofinanz," he added.
Pecik's term as chief executive lasts three years and begins on May 4, Immofinanz said.
(Reporting by Francois Murphy; Editing by Emelia Sithole-Matarise)