Stuart McCullagh drove to the Cuckoo Birch pub, on Jubilee Way South, after a “hysterical” call from his brother Daniel’s girlfriend at 8pm.
“He was waving the hammer about and asking where his brother was,” said Neil Hollett, prosecuting.
Police were called to the pub after a complaint was made about Daniel, he said, but no further action was taken about it.
“Understandably his brother’s partner panicked,” said Sarah Neale, mitigating.
“He was anticipating a brawl and without really thinking about what he was doing he took a hammer from the boot of his car. He didn’t quite know what he was going to come across.”
He found his brother Daniel was injured in Tesco car park, she said, and took him back the pub where the pair were arrested.
Stuart McCullagh, 28, admitted possession of an offensive weapon, and Daniel McCullagh, 26, admitted being drunk and disorderly, when they appeared at Mansfield Magistrates Court on Wednesday.
Both brothers live with their parents on Whaley Bridge Close, Mansfield.
Daniel, a freeelance agency worker, was fined £100 and ordered to pay costs of £85 and a victim surcharge of £30.
Stuart, an odd job man, was given a 12-month community order, with 100 hours of unpaid work and ten days of a rehabilitation activity requirement.
He was ordered to pay costs of £85 and a victim surcharge of £85.