A 26,000-strong crowd rocked up at Stadium MK to cheer on Sarina Wiegman's team, but the Lionesses faithful were subjected to a frustrating afternoon as England went two games without a win following their loss to Australia in April.
Wiegman's decision to start Rachel Daly over Alessia Russo at the tip of the attack dominated the pre-game discussions, and the Lionesses tried to use the Aston Villa attacker's aerial dominance to their advantage early doors.
With just five minutes on the clock, Portugal goalkeeper Ines Pereira was forced into a strong save down low to keep out a Daly header, and the England attacker had a second bite at the cherry not long after; her retry was meat and drink for Pereira, though.
England unsurprisingly continued to control the game, but Wiegman's side largely struggled to make inroads against a well-drilled Portugal backline, who survived a late scare as a Lauren Hemp cross found Georgia Stanway, and the latter's injury-time effort deflected off the bar.
Wiegman responded at the break by bringing on Russo as part of a triple change, also introducing Chloe Kelly and Niamh Charles as Ella Toone, Daly and Alex Greenwood - who suffered a knock in training earlier this week - made way.
Russo and Kelly's introductions in particular breathed new life into England, and the former was presented with a magnificent chance to draw first blood in the 58th minute - skipping past Pereira after latching onto Lauren James's through ball - but Ana Borges raced back to hook Russo's goal-bound effort off the line.
From the resulting corner, Lucy Bronze crashed a header against the woodwork from Stanway's corner, before Russo dragged another attempt just wide of the post from Kelly's cutback in the 61st minute as England upped the ante.
The Lionesses' incessant pressure would not let up, but Russo - now a free agent after leaving Manchester United - was guilty of wasting another couple of chances to break the deadlock, while Hemp and Mary Earps experienced a heart-in-mouth moment from the former's backpass, which Earps misjudged but gratefully watched trickle just past the post.
Five minutes of added time went up on the fourth official's board, and Portugal remained under the cosh in the dying embers, but there was still no way through for Wiegman's charges.
England now prepare to travel Down Under ahead of their World Cup opener versus Group D rivals Haiti in three weeks time, before the Lionesses tackle Denmark and China on July 28 and August 1 respectively.
Meanwhile, Portugal have been handed a daunting draw against reigning champions USA, 2019 runners-up Netherlands and Vietnam in Group E, and Francisco Neto's side kick off the World Cup against the Netherlands on July 23.