National Super Alliance (Nasa) flag bearer has the podium to himself as President Uhuru Kenyatta skipped the presidential debate.
Mr Odinga arrived a few minutes to 8pm but the debate started 30 minutes later after President Kenyatta failed to show up.
Both Mr Odinga and President Kenyatta had said they will not attend the debate.
But Mt Odinga showed up accompanied by his wife Ida, co-principal Musalia Mudavadi and Machakos Senator Johnson Muthama.
State House digital boss Dennis Itumbi criticised the organisers in a series of tweets Monday morning, accusing them of advertising that candidates were coming for the debate without having confirmed with them.
Alliance for Real Change (ARC) flag-bearer Mohammed Abduba Dida also did not participate in Monday’s presidential debate, citing media bias.
Two other candidates, Joe Nyaga (independent) and Cyrus Jirongo (United Democratic Party) also skipped the debates.