It has received undertakings from the majority shareholders to sell 50.08 percent of the voting rights and 38.10 percent of the capital.
Capio is offering 57.50 Swiss francs (330 kronor) per Unilabs bearer share and 28.75 sfr per registered share to minority shareholders.
The offer price carries premiums of 30.3 percent over the weighted average price for the past 60 days and of 27.3 percent respectively.
Financing for the deal has been secured and the offer is expected to be completed before year-end.
The companies said the combined entity will carry the Unilabs name and have its headquarters in Geneva.
Paul Hokfelt, president and CEO of Capio, said: “The companies are a perfect fit with over 100 laboratories and testing facilities across Europe.”
Based on their latest full-year results, the combined group would have pro forma sales of over 510 million sfr and about 2,800 employees.