Osagie won 800m bronze at the last World Indoor Championships in Istanbul in 2012 and was one of three Brits to enjoy a successful first morning at the Ergo Arena.
Drawn in the third of three heats, the 26-year-old finished second behind Polish home hope Adam Kszczot in 1:45.88 minutes; those two the quickest overall into the final.
Osagie will have to wait until Sunday to return to the track at the Ergo Arena but, after safely advancing out of the heats, he's confident he can medal again.
"A lot of athletes talk about saving something for the final but there is no point doing that if you don't get into the final," said Osagie.
"I thought I was capable and luckily I went fast and felt strong and I am looking forward to the final now. I am making a habit of reaching finals.
"I am really enjoying myself and I always believe in myself and give 100 per cent. The heats were more nerve racking because I have got a medal to defend.
"And to do that I needed to make the final but it is a great place to be and I would rather it be like that than the other way around."
Osagie was joined in the 800m heats by Mukhtar Mohammed but he placed fourth in the first heat and missed out although his time of 1:47.59 was a season's best.
Margaret Adeoye and Nigel Levine were the two other Brits to advance out of their 400m heats in Sopot, both now set for semi-final action later in the evening.
The same could not be said for Shana Cox and Richard Buck in the same 400m heats while Chris O'Hare and Lee Emanuel went out in the 1500m heats; Laura Muir suffering that fate in the 800m
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- Adam Kszczot