Well then you have something else going on. We are at an extreme disadvantage since we don't know your table structures.

The following code works just fine.

if OBJECT_ID('tempdb..#MyData') is not null

drop table #MyData

create table #MyData

(

SomeVal varchar(10)

)

insert #MyData

select '10' union all

select '125' union all

select '-4.67625' union all

select 'abc'

select * , case SomeVal when '-4.67625' then 2 when 'abc' then 1 else CONVERT(decimal(20,6), SomeVal) end

from #MyData

From what you have posted that is as close as I can get to your issue here. I can't imagine why you are getting the convert to int error since you said you are converting to decimal. If you can post the table structure and the entire query you running it will help understand what is going on.