The landscapes in both New Zealand and on a trip Passenger took in Iceland lent inspiration to the creation of a newly panoramic album, with themes of relationships and the passing of time that are at once personal and universal.

Reviewing for AllMusic, Matt Collar commented, "Ultimately, with Young as the Morning Old as the Sea, Passenger has crafted an album that, not unlike the oceans, fields, roads, and relationships that inspired it, remains with you, calling you to return.

"[5] David Smyth of the London Evening Standard wrote, "As Passenger, the solo artist achieved a slow-burning worldwide hit with his pretty break-up song Let Her Go, and has followed it with similarly tasteful fare.

There isn’t a single singalong number trying to set up camp in your temporal lobe on Young As the Morning Old As the Sea – it seems that in his hurry to vacate the trodden ground of campfire pop, Michael Rosenberg hasn’t really planned where to go.

"[8] Lauren Murphy of The Irish Times wrote, "His “If it ain’t broke, don’t fix it” approach means that songs such as Everything and Fool’s Gold lumber pleasantly but forgettably along, while the addition of Birdy on vapid duet Beautiful Birds makes scant difference.