Hitachi chairman Hiroaki Nakanishi told the Telegraph he voiced concerns about Wylfa Newydd's expected cost to Foreign Secretary Philip Hammond.
It followed problems a rival faced for the Hinkley Point plant in Somerset.
The UK government said it wants low-cost nuclear power.
Hitachi owns Horizon Nuclear Power which is behind the plans to build the new power plant, which could be operational by the early 2020s.
Horizon is in talks with the Department of Energy and Climate Change (DECC) on issues such as the strike price, which will be key to attracting additional finance.
Mr Nakanishi said Hitachi had set out "very fair conditions for the making of our investment", but could only commit to a deal it believed was viable.
"Hinkley Point [raises questions] about what are the real solutions for setting up financial support," he told the Telegraph.
"We need to arrange a financial plan for which the kind of money needed can be introduced.
Mr Nakanishi said the challenges faced by the £18bn Hinkley Point project could also affect Horizon.
He added: "The DECC worries about the stability of the scheduled construction of the [Hinkley Point] nuclear power plant, so some of the conditions - the credit requirements - those kind of things may affect us.
"In order to set up the financial conditions [to build Hinkley], Chinese capital was introduced, but what the real result will be - we have a very serious concern about that."
Asked if Hitachi might step back if it believed a viable deal was not on the table, Mr Nakanishi replied: "Yes".
But Alan Raymant, chief operating officer of Horizon, said Wylfa talks were "progressing rapidly with the solid backing of Hitachi".
Energy Secretary Amber Rudd said: "The challenge, as with other low carbon technologies, is to deliver nuclear power which is low cost as well."
The head of the company behind a new £8bn nuclear power station on Anglesey has warned it may walk away from the project if a subsidy deal with the UK government cannot be reached.