If I do Diploma in Mechanical Engineering, then can I do MBA without and Bachelor's Degree?

Dear Umang, Mr. Karmaveer has rightly answered your question but in addition to it I would like to tell you that there's a way out for you. After completing diploma you have an option to give a test which equalizes your diploma to +2 and on the basis of +2 you can opt for graduation an then further

Not at all. MBA means Master Degree In Business Adminstration you should do first Bechlor's Degree in Mechanical Engineering than you can do MBA in Operation Management or Material Management or Marketing Management.

After a diploma you are not eligible for applying in MBA program offered by any university/ autonomous institutes but you can do MBA from IGNOU after having six years of professional experience. Also you need to clear the entrance test conducted by IGNOU.