The multi-year deal will see Netflix servers connected directly to Comcast’s network, removing third parties that slow down streaming speeds.
However, Comcast said Netflix would not get “preferential network treatment”.
The terms of the deal, including whether Netflix was paying for it, were not disclosed by the firms.
“The companies have established a more direct connection between Netflix and Comcast, similar to other networks, that’s already delivering an even better user experience to consumers, while also allowing for future growth in Netflix traffic,” Comcast said in a statement.
The move comes just days after Comcast confirmed a deal to acquire Time Warner Cable for about $45bn (£27bn).
According to some estimates, the combined company would control more than one-third of the US high-speed internet market.
Netflix, a TV and movie streaming service, has 44 million subscribers – majority of them in the US.
The deal may see the firm enter similar deals, known as interconnect agreements, with other internet service providers across the country.