Local politicians and some staff have voiced concern that it could affect workers' jobs and lead to an increase in customers' bills.
About 20 opponents waving banners made their views known outside the meeting.
Severn Trent Water said it plans to build on Dee Valley's customer service record and make a "significant" investment in the region.
Dee Valley Water employs about 180 people and has 230,000 customers across the Wrexham and Chester areas.
Customers pay an average of £145 a year for their water compared with £172 for Severn Trent.
Severn Trent Water have outbid London investment firm, Ancala, which offered about £78.5m.
About 120 Dee Valley shareholders met at Wrexham's Ramada Plaza hotel to cast their votes, although some do not know yet if their votes will count.
Dee Valley is seeking clarity after one shareholder transferred ownership of more than 400 shares to individuals.
A court hearing to establish the validity of the votes and sanction the takeover is due to take place later this month.
Plaid Cymru and Labour politicians oppose the possible takeover with Wrexham MP Ian Lucas saying Severn Trent was "not welcome".
He said: "We wonder why it is that Severn Trent want to acquire Dee Valley Water and I think the short answer to that is that they want to pay more money to their shareholders.
"We are happy with things as they are. We want it to stay that way."'
A spokesman for Seven Trent said it was the "best long long-term owner for Dee Valley".
"We have always said we are committed to maintaining front line field force operations in Wrexham and Chester," the spokesman said.
"We have already met with Dee Valley employees since we announced our offer and attach great significance to their skills and operational and technical expertise."
Shareholders in Wrexham's Dee Valley Water company have met to vote on an £84m takeover by Severn Trent Water.