If adopted, the new presidential regime will hand the Turkish President extra powers including greater opportunities to dissolve Parliament, declare a state of emergency and appoint ministers.
The parliamentary assembly of the Council of Europe, known as PACE, plans to send a 20-member delegation to Turkey to observe this weekend's referendum.
The Strasbourg-based body says this follows an invitation from the Turkish authorities themselves.
PACE members will meet Yes and No campaigners in Turkey, as well as political leaders, NGOs and media figures.
More than 55 million Turkish citizens will vote on Sunday in the referendum on constitutional changes.
Over 1.2 million Turkish expatriates have already voted at 120 polling stations in 57 countries since 27 March.
The proposed constitutional changes seek to transform Turkey's current system to an executive presidential system.
President Recep Tayyip Erdoğan, his Justice and Development Party (AK Party) and far-right Nationalist Action Party (MHP) say the new system will make Turkey more efficient and stable.
The main opposition, the Republican People's Party (CHP), pro-Kurdish People's Democracy Party and other critics argue the amendments will give too much power to one individual, undermining the separation of powers in the government.
Turkey has been under a state of emergency since a group in the Turkish army tried to overthrow the government in a failed coup attempt that killed around 300 people.
Ankara's relations with the European Union, particularly with Germany and the Netherlands, have been tense since last month after the two member states barred Turkish ministers from rallying at referendum campaign gatherings within their borders, where millions of Turkish voters live.
In an interview Sezgin Tanrıkulu, a senior CHP MP who leads the party's No campaign, said, "We accept that the parliamentary system in Turkey has its flaws.
"However, the AK Party's proposal has the potential to deepen the problems in the system, rather than solve them. Turkey has been governed with a parliamentary system for over 100 years. Throwing away this tradition will not solve anything."
He added, "The AK Party is trying to introduce a freak unprecedented 'presidential system', while practically abolishing the parliamentary system."