Chief executive Karl Koehler is standing down and his replacement will not have a position on the main Tata board in Mumbai, unlike Mr Koehler.
Tata is making 1,050 people redundant, including 750 at its Port Talbot site.
Community organiser Rob Edwards said he was surprised by Mr Koehler's departure and what it meant for the future.
"I think it compounds the recent news about the redundancies. You start to ask questions about long-term investments," said Mr Edwards.
"There is an element of doubt, we walk a path of uncertainty," he told BBC Radio Wales's Wales at Work programme.
He added that he wasn't concerned about the short-term commitments made by the company as it tries to save Â£300m as part of its current survival plan.
He said the union was worried that the move weakened the voice of the European operation when it came to decisions being made by the board in future.
Workers from Tata marched through Brussels with Mr Koehler and steelworkers from across Europe demanding that the EU take action on the price of Chinese imports.
New chief executive of Tata Steel Europe, Hans Fischer, takes over on 1 March.
Koushik Chatterjee, the group executive director for finance and corporate affairs, will add responsibility for Europe to his role on the Tata Steel board in Mumbai.
Changes at the top of Tata Steel Europe raise doubts about the "long-term investment" of the company, according the steelworkers union, Community.