A strong Castleford team scored eight unanswered tries to race into a 48-0 lead at the break.
But the Dons could take plenty of heart from a second half which saw both sides score three converted tries.
Misi Taulapapa, Zac Braham and Tom Halliday touched down for Doncaster with Connor Robinson adding the extras.
Doncaster host Thornhill Trojans in the second round of the Betfred Challenge Cup on Sunday.
Dons: Taulapapa, Halliday, Smeaton, Storey, Corrion, Johnston, Robinson, Fella, Burns, Braham, Ollett-Hobson, York, Peterson. Interchanges: Sanderson, Whitmore, Seaman, Ruan, Roberts.
Castleford: Evalds, Olpherts, Fonua, Mamo, Faraimo, Trueman, Richardson, Lawler, Robb, Massey, Blair, Edwards, Westerman. Interchanges: Turner, Marris, Sutcliffe, Griffin, Hepi, Clare, Smith, Morley, Matagi, Vasuitoga, Martin, Hall, Brennan-Jones, Ransome, Qareqare, Sadler, Carter, Collins.
. Picture: Andrew Roe/AHPIX LTD, Rugby League, Pre Season Friendly, Doncaster Dons RLFC v Castelford Tigers, Eco Power Stadium, Doncaster, UK, 23/01/22, K.O 3pm Dons' players celebrate Misi Taulapapa's try
Dons players celebrate Misi Taulapapa's try. Picture: Andrew Roe/AHPIX LTD Photo: Andrew Roe/AHPIX LTD
. New boy
Dave Peterson made his first appearance for Doncaster. Photo: Andrew Roe/AHPIX LTD
1. New boy
Dave Peterson made his first appearance for Doncaster. Photo: Andrew Roe/AHPIX LTD
4. Storey time
Robbie Storey was another debutant for the Dons. Photo: Andrew Roe/AHPIX LTD