The Ponds Forge-based athletes represented Team GB alongside Noah Williams and Eden Cheng in the Mixed Synchronised 10m final in Budapest, Hungary on Monday evening.
They recovered from last place after the second round to finish fourth behind Russia, Italy and Germany and one place ahead of Ukraine.
Each team had to perform total of six dives – three from the 3m springboard comprising of one man, one woman and one synchro and the same from the 10m platform.
Meanwhile, Sheffield-based diver Clare Cryan who represents Ireland, will not be going to the Tokyo Olympics this summer after she missed out on the qualification spots in the 3M Springboard event at the delayed FINA Diving World Cup.
She will be back in action at the six-day-long European Championships event on Tuesday evening when she takes part in the 1M Springboard final, having finished sixth in the preliminary round this morning.
Harper, aged 20, finished twenty-third and missed out on a spot in the final.
Cryan, 27, will also compete in the 3M Springboard on Thursday. Haslam, 23, is back in diving action in the Men’s 1M Springboard on Wednesday and will also take part in the Mixed Synchronised 3M final with Harper tomorrow.
There are no preliminary rounds in the synchro and team events at the European Championships, only finals are held.
The European Diving Championships form part of the European Aquatics Championships that also includes swimming, open-water swimming and synchronised swimming.