How much is a ticket from Lisbon to Porto?

The cheapest price found today is $52.

When is it cheaper to fly?

Cheapest month is October — from $52.

Cheapest today — $52. Below is what booking services offer.

Departure	Airline	Stops	Price
Oct 2	TAP Air Portugal	direct	$52	View
Aug 24	TAP Air Portugal	direct	$53	View
Aug 25	TAP Air Portugal	direct	$54	View
Sep 10	TAP Air Portugal	direct	$55	View
Nov 23	TAP Air Portugal	direct	$57	View
Nov 24	Portugalia Airlines	direct	$57	View

How much is a ticket from Lisbon to Porto?: The cheapest price found today is $52.
When is it cheaper to fly?: Cheapest month is October — from $52.

Links to booking services are affiliate links. The price stays the same for you.