The offer is valued at $19.45 per Inter Pipeline share based on the closing price of Pembina shares on Monday. Inter Pipeline shares closed at $17.55 but increased $1.53 or 8.7 per cent at $19.08 in afternoon trading on the Toronto Stock Exchange
The deal tops the offer made by Brookfield that was valued at $16.50 per share.
In March, CEO Chris Bayle said the Brookfield bid undervalued their business.
"After a comprehensive review of strategic alternatives by the special committee of the board of directors of Inter Pipeline, it was evident that a combination with Pembina offered compelling value for Inter Pipeline shareholders in the short-term," said Margaret McKenzie, Inter Pipeline's chairwoman.