The Dutchwoman won the 1500m title in Amsterdam two years ago and came close to clinching the 1500m-5000m double in Zurich in 2014 when she was outsprinted in the longer race by Sweden's Meraf Bahta.
Her hopes of going for a double in Berlin have been dashed by the timetable, with both events finishing on the same evening.
Hassan took world championship bronze in the 5000m last August and lowered the European record to 14 minutes 22.34 seconds in Rabat last month, making her the fastest European of 2018 by half a minute.
Britain's Eilish McColgan is the only other European under 15 minutes this year.
Turkey's reigning champion Yasemin Can will be attempting another 5000m-10,000m double, while Israel's rapidly improving Lonah Chemtai Salpeter will be a contender in both after winning the European 10,000m Cup in London in May in a world-leading time of 31:33.03.
German favourite Konstanze Klosterhalfen has opted to step up to the 5000m after winning the European under 23 1500m title last year. She has struggled with a knee injury this season but won the German 1500m title in Nurnberg.
With Hassan focused on the 5000m, the path should be clear for Laura Muir to win her first major outdoor title in the 1500m. The Briton won the 1500m-3000m double at the Belgrade 2017 European Indoor Championships, but missed out on a medal at last year’s world championships in London by just 0.08 seconds.
Muir won two medals at the world indoor championships in Birmingham in March and has the quickest time in the field this year ahead of team-mate Laura Weightman, although a minor Achilles tendon injury put paid to her hopes of going for the 800m as well.
The favourites in that event are Ukraine's reigning champion Nataliya Pryshchepa, 2016 silver medallist Renelle Lamote of France, and Britain’s 2012 champion Lynsey SHARP, who have all broken the two minute-barrier in 2018.
Gesa-Felicitas Krause will defend her title in the 3000m steeplechase although the German has not been in top form so far this season.
The quickest European this year is Karoline Bjerkeli Grovdal (NOR) who made a terrific comeback in 2017 after a seven-year hiatus.
Behind her sits Luiza Gega, who won Albania's first European championship medal in Amsterdam two years ago when she was second.