Sixty per cent of ABC staff who took part in a vote rejected the offer, paving the way for a range of industrial actions including a 24-hour strike.
The strike is set for 11am on Wednesday and is expected to impact live broadcasts on both television and radio.
While non-media staff walked off the job in 2023, journalists did not take part.
This time, the strike won 90 per cent support among voting media-union members.
The union said below‑inflation pay outcomes and ongoing insecure work threatened the future of public‑interest journalism.
ABC management's last offer was confirmed as being rejected on Monday.
It featured limited job security, did not address concerns around staff being stuck on rolling short-term contracts and failed to guarantee jobs would not be cut and replaced by AI, the media union said.
"Experienced journalists and media workers are being asked to do more with less - with fewer opportunities for pay progression, less certainty about their future, and growing workloads," Media, Entertainment and Arts Alliance chief executive Erin Madeley said.
"This isn't just a workforce issue. When skilled, experienced staff are forced out, communities lose trusted local voices, particularly in regional Australia where the ABC is often the only local newsroom."
Strike action was also backed by a ballot of non-media ABC staff, represented by the Community and Public Sector Union.
Staff rejected the deal because it featured a pay rise below inflation, along with concerns about career progression, night-shift penalty rates and reproductive health leave, the union said.
"The last thing union members want to do is inconvenience loyal ABC audiences by disrupting programming and services, but key bargaining claims remain unresolved," the union's ABC section secretary, Jocelyn Gammie, said.
"Unless the ABC put a fair offer on the table, disruptions are inevitable."
More than 4400 people work at the ABC, including 2000 in news, the largest division.
ABC is the 11th most used website in the nation ahead of Netflix, according to SimilarWeb.
ABC's chief people officer Deena Amorelli emailed staff on Monday to inform them the deal had been declined.
"The ABC will now make an application to the Fair Work Commission to assist with resolving bargaining," she said.
"Further information about next steps, including proposed strike action by MEAA and the CPSU, will be communicated over the next couple of days."
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