This is how you chain custom methods on custom manager ie: Post.objects.by_author(user=request.user).published()

from django.db.models.query import QuerySetclass PostMixin(object):    def by_author(self, user):        return self.filter(user=user)    def published(self):        return self.filter(published__lte=datetime.now())class PostQuerySet(QuerySet, PostMixin):    passclass PostManager(models.Manager, PostMixin):    def get_query_set(self):        return PostQuerySet(self.model, using=self._db)

Link here : django-custom-model-manager-chaining

Note :

In Django 1.7 you have this out of the box . Check out QuerySet.as_manager

Looks like this snippet provides a solution to your situation: Custom managers with chainable filters.

Just a code example using the new as_manager() method (see update information from @zzart.

class MyQuerySet(models.query.QuerySet):    def randomize(self):                count = self.aggregate(count=Count('id'))['count']        random_index = random.randint(0, count - 1)        return self.all()[random_index]class MyModel(models.Model):    .....    .....    objects = MyQuerySet.as_manager()    .....    .....

And then you will be able to use something like this in your code:

MyModel.objects.filter(age__gt=16).randomize()

As you can see, the new as_manager() is really neat:)