AirHint found the following cheapest return flights from Washington (IAD) to Madrid (MAD) in September 2025 (see full year).

Return flights

29 Sep - 08 Oct	TAP
21 Sep - 20 Oct	TAP
16 Sep - 24 Sep	TAP
30 Sep - 22 Oct	TAP
29 Sep - 06 Oct	TAP
25 Sep - 08 Oct	TAP
25 Sep - 07 Oct	TAP
22 Sep - 01 Oct	TAP
25 Sep - 06 Oct	TAP
16 Sep - 30 Sep	TAP
10 Sep - 17 Sep	TAP
08 Sep - 17 Sep	TAP
29 Sep - 08 Oct	American Airlines	direct
30 Sep - 30 Oct	Iberia	direct
10 Sep - 18 Sep	TAP
07 Sep - 16 Sep	TAP
22 Sep - 29 Sep	Air Canada
15 Sep - 23 Sep	TAP
17 Sep - 24 Sep	Iberia	direct
21 Sep - 29 Sep	Air Canada

Also check the deals for one-way flights from Washington to Madrid in September.

The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.

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Cheapest return flights from Washington to Madrid in September from $333

Return flights