A bar worker stole £10 from a colleague's rucksack and kept a mobile phone which was left in the Pryzm club.
The two offences left 20-year-old Casey Stewart being told by a judge that it was "a significant breach of trust."
A £300 fine and costs of £117 must be paid by Stewart of Porchester Road, Nottingham. He was dismissed when the offences were discovered on September 29.
Sitting at Nottingham Magistrates' Court, District Judge Tim Spruce went on: "You have let yourself down coming before the court when you have never been in trouble before. Make sure it is not repeated.
"These two theft matters involve a significant breach of trust - you are stealing from colleagues you work with.
"If you can't trust people you work with, it is a sad state of affairs. What would be the effect if someone was messing about with your bag?"
Stewart replied: "Upset."
Sanjay Jerath, prosecuting, said that a woman employee noticed that her rucksack had been tampered with when she went into the staff room at 2.45am to get some Paracetamol. A £10 note had gone from her purse.
Stewart was questioned and admitted taking it. He had another £5 which he said were tips.
He also had a rose gold iPhone 8. Mr Jerath added: "He said that he found it a couple of weeks ago. He found it and had not reported it."
Stewart pleaded guilty to theft of £10 at Pryzm and theft of the phone "of a value unknown, belonging to an unknown person."
He told the court: "I regret it." He now has two jobs, one in a bar and one in a shop.
