In the talks in London on Thursday, the Italian MEP will discuss Parliament's position on Brexit.
This was spelled out in a recently adopted resolution defining key principles and conditions for its approval of the UK's withdrawal agreement.
Any such agreement at the end of UK-EU negotiations will need to win the approval of Parliament.
The resolution warns against any trade-off between security and the future EU-UK economic relationship, opposes any sort of cherry picking or a piecemeal economic relationship based on sector-specific deals, and reiterates the indivisibility of the four freedoms of the single market - free movement of goods, capital, services, and people.
It says the UK will continue to enjoy its rights as a member of the EU until its departure. At the same time, however, it will also have to shoulder its obligations, including financial obligations
Speaking ahead of the meeting with May, Tajani said, "Defending the rights of our citizens is our first priority and as the directly elected representatives of millions of EU citizens affected by the UK's departure, the European Parliament will carry out this responsibility with the utmost diligence."
The EPP group deputy added, "Students, workers and families, some of whom have spent their entire lives in another EU country, deserve absolute certainty over their future."
He said the European Parliament will have a decisive role in determining the outcome of the negotiations and all parties involved are urged to take on board the Parliament's concerns.