The 21-year-old hasn't played a single Premier League game for the Gunners following his move to north London from Legia Warsaw In 2015.
But an excellent loan spell at Charlton last season, where he helped the Addicks win promotion to the Championship, saw his stock rise dramatically.
Arsenal had hoped to convince the central defender - who can also play in midfield - to sign a new contract at the Emirates before heading out on loan again.
But Bielik made it clear that he had no interest in spending another season on loan and that he wanted a permanent move, if he wasn’t going to get a chance under Unai Emery.
Speaking before this summer’s U-21 European Championship, Bielik told the Polish media: "My future is unknown but there is one thing I can say for sure: I will definitely not go back to the Arsenal U-23 team.
"At this stage it wouldn’t make sense.
"If I do not receive the possibility to join the first team permanently, I will have to look for other solutions.
"I feel like a senior player now so I want to play senior football.
"This is, however, not the right moment to discuss these issues as I want to be 100 per cent focused on the European Championship."
Arsenal have had plenty of interest in Bielik this summer, with several Championship clubs keen, while AC Milan were also linked with a potential move.
But the centre-back now looks set for a switch to Derby after the Gunners agreed a deal with the Rams that could eventually reach £10m with add-ons.
Bielik will undergo a medical today with the Championship side before finalising his move to Pride Park.
The deal comes soon after Arsenal sold teenage attacker Xavier Amaechi to Hamburg for a fee £2.25m and adds valuable money to the club’s transfer budget, with one week remaining of the summer window.
Arsenal - who will announce the £72.5m ($88m) capture of Ivory Coast winger Nicolas Pepe imminently - are in talks with Celtic for left-back Kieran Tierney.
The Scottish champions have already knocked back two bids for the 22-year-old and are standing firm in their £25m valuation.
Negotiations are continuing, with Emery desperate to land Tierney, who is understood to be keen on speaking to the Gunners about a switch to the Premier League.
And the imminent sale of Bielik could give Arsenal the extra cash they need to finally get the deal for the defender over the line.